fix(e2e): converge Amazon Linux 2 AMI with its batteries-included -e2e variant

[chouetz]

https://datadoghq.atlassian.net/browse/ACIX-2049
https://datadoghq.atlassian.net/browse/ACIX-2096

What does this PR do?

Repoints the default Amazon Linux 2 AMI in platforms.json (both arm64 and x86_64) to the batteries-included image built by ami-builder, instead of leaving the "2-e2e" entries unused. Also removes a dead AmazonLinux case from installAnsible() in installer/unix/all_packages_test.go.

Motivation

The "2-e2e" AMI already ships with Docker, jq, ansible, awscli etc. pre-installed (provision-e2e-amazon-linux.sh), but nothing in datadog-agent referenced it — no Go const, no CI descriptor string. Meanwhile every AmazonLinux2 test in the installer/unix and installer/script apm-inject/all-packages suites pays a real yum install -y docker at runtime via host.Host.InstallDocker(), which becomes a no-op once the AMI is baked. Converging the plain "2" and "2-e2e" entries removes that redundant runtime install without introducing a separate e2e flavor, mirroring the Debian 11/12 convergence in #56516.

We deliberately did not remove the InstallDocker() call sites themselves: the function already guards the actual package install with a command -v docker check (so it's already a no-op on the baked AMI), and it also performs required ECR-credential-helper setup and a clean docker restart on every call, for every flavor in the shared flavor lists (Ubuntu, Debian, RedHat, CentOS, Suse) — not just Amazon Linux. Removing the calls would strip that always-needed setup for flavors that aren't baked.

While investigating, we found that installAnsible()'s case e2eos.AmazonLinux, e2eos.RedHat: branch is unreachable for AmazonLinux: RunInstallScript skips InstallMethodAnsible for AmazonLinux2 before installAnsible is ever called, and no flavor list in the repo uses AmazonLinux2023. RedHat9 is the only flavor that actually executes that branch, so we removed AmazonLinux from the case.

Describe how you validated your changes

Grepped the repo to confirm the removed "2-e2e" AMI keys had no remaining Go-const or CI-descriptor references, and confirmed platforms.json stays valid JSON. Traced every call site of InstallMethodAnsible/installAnsible to confirm the removed AmazonLinux case was truly unreachable. We'll also run a full pipeline on this branch to validate end-to-end.

[github-actions]

AI review by Codex (OpenAI) - workflow run

The patch is correct. Both architectures now use their existing e2e AMIs, and no repository references depend on the removed 2-e2e keys. JSON validation passed; no actionable regressions found. AMI availability and provisioning were not verified against AWS.

[datadog-datadog-prod-us1]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 58.48% (+1.77%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 808850c | Docs | Give us feedback!}

[github-actions]

AI review by Codex (OpenAI) - workflow run

The patch is correct. No actionable regressions found: both architectures reuse the existing E2E AMIs, and Amazon Linux 2 skips Ansible before reaching the removed case. JSON validation passed. AMI provisioning and E2E execution were not verified.

[dd-octo-sts]

Files inventory check summary

File checks results against ancestor 248a7560:

Results for datadog-agent_7.85.0~devel.git.521.808850c.pipeline.139199486-1_amd64.deb:

No change detected

Results for datadog-iot-agent_7.85.0~devel.git.521.808850c.pipeline.139199486-1_amd64.deb:

No change detected

[guohdd]

LGTM from Windows perspective (no impact).

[cit-pr-commenter-54b7da]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Job ID: 426293a7-443f-45ac-8288-547d27c7b9e2

Baseline: 35a3649
Comparison: e32d2ff
Diff

Optimization Goals: ✅ No significant changes detected

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
➖	quality_gate_logs	% cpu utilization	+3.35	[+2.48, +4.23]	1	Logs bounds checks dashboard
➖	dsd_uds_10mb_3k_timestamped_contexts_memory	memory utilization	+0.75	[+0.54, +0.96]	1	Logs
➖	dsd_uds_10mb_3k_timestamped_contexts_cpu	% cpu utilization	+0.56	[+0.32, +0.79]	1	Logs
➖	quality_gate_security_mean_fs_load	memory utilization	+0.42	[+0.38, +0.46]	1	Logs bounds checks dashboard
➖	quality_gate_metrics_logs	memory utilization	+0.25	[+0.02, +0.48]	1	Logs bounds checks dashboard
➖	quality_gate_security_no_fs_load	memory utilization	+0.20	[+0.12, +0.28]	1	Logs bounds checks dashboard
➖	quality_gate_idle	memory utilization	+0.20	[+0.16, +0.24]	1	Logs bounds checks dashboard
➖	quality_gate_private_action_runner	memory utilization	+0.16	[+0.03, +0.28]	1	Logs bounds checks dashboard
➖	quality_gate_idle_all_features	memory utilization	-0.07	[-0.11, -0.04]	1	Logs bounds checks dashboard
➖	quality_gate_security_idle	memory utilization	-0.28	[-0.31, -0.24]	1	Logs bounds checks dashboard

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	observed_value	links
✅	quality_gate_idle	intake_connections	10/10	4 ≤ 5	bounds checks dashboard
✅	quality_gate_idle	memory_usage	10/10	176.16MiB ≤ 179MiB	bounds checks dashboard
✅	quality_gate_idle	total_bytes_received	10/10	746.49KiB ≤ 819.20KiB	bounds checks dashboard
✅	quality_gate_idle_all_features	intake_connections	10/10	4 ≤ 5	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	517.42MiB ≤ 537MiB	bounds checks dashboard
✅	quality_gate_idle_all_features	total_bytes_received	10/10	1.14MiB ≤ 1.25MiB	bounds checks dashboard
✅	quality_gate_logs	intake_connections	10/10	18 ≤ 40	bounds checks dashboard
✅	quality_gate_logs	memory_usage	10/10	211.77MiB ≤ 228MiB	bounds checks dashboard
✅	quality_gate_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_logs	total_bytes_received	10/10	263.30MiB ≤ 292MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	cpu_usage	10/10	361.24 ≤ 2000	bounds checks dashboard
✅	quality_gate_metrics_logs	intake_connections	10/10	20 ≤ 40	bounds checks dashboard
✅	quality_gate_metrics_logs	memory_usage	10/10	409.85MiB ≤ 455MiB	bounds checks dashboard
✅	quality_gate_metrics_logs	missed_bytes	10/10	0B = 0B	bounds checks dashboard
✅	quality_gate_metrics_logs	total_bytes_received	10/10	0.94GiB ≤ 1.04GiB	bounds checks dashboard
✅	quality_gate_private_action_runner	memory_usage	10/10	72.56MiB ≤ 75MiB	bounds checks dashboard
✅	quality_gate_security_idle	cpu_usage	10/10	31.32 ≤ 100	bounds checks dashboard
✅	quality_gate_security_idle	memory_usage	10/10	326.26MiB ≤ 355MiB	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	cpu_usage	10/10	63.58 ≤ 200	bounds checks dashboard
✅	quality_gate_security_mean_fs_load	memory_usage	10/10	309.26MiB ≤ 335MiB	bounds checks dashboard
✅	quality_gate_security_no_fs_load	cpu_usage	10/10	23.21 ≤ 100	bounds checks dashboard
✅	quality_gate_security_no_fs_load	memory_usage	10/10	318.89MiB ≤ 345MiB	bounds checks dashboard

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

• quality_gate_security_mean_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_mean_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_no_fs_load, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_no_fs_load, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_private_action_runner, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_metrics_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check cpu_usage: 10/10 replicas passed. Gate passed.
• quality_gate_security_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check missed_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check intake_connections: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check total_bytes_received: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.