Switch the easymongo test suite to easymongotest

[TopherGopher]

Part of the easymongo refactor (see PLAN.md on the refactor branch). Agreed with the maintainer: keep one container per test function; do not consolidate into a shared container.

Working context (read this first)

• Repository github.com/tophergopher/easymongo. Start from branch claude/mongotest-easymongo-refactor-wu2vhm; create a branch issue-<number>-<short-slug> from it and open a pull request back into it. PLAN.md on that branch is the source of truth; read it before writing code.
• Go project, single module, all packages at the repo root except the new easymongotest/ subpackage. The final toolchain target is Go 1.27 (set by Toolchain: go 1.27, latest dependencies, tidy, remove replace directives #10); any Go 1.24 or newer works until then. Before pushing: gofmt -l . prints nothing, go vet ./..., go test -race ./....
• The existing test suite (*_test.go at the root, package easymongo_test, every test function calling setup(t) from common_test.go) is the regression net for this refactor. It must pass after your change. It needs a Docker daemon reachable through the normal Docker environment and the mongo:8 image.
• Order matters. The driver package cannot compile half-migrated (the *mongo.Client type flows from Connection to Database to Collection), so the four driver issues Driver v2: migrate connect.go (mongo.Connect, Disconnect, BSONOptions, write concern) #2, Driver v2: options struct literals become builders; drop MaxTime; ArrayFilters and Delete option changes #3, Driver v2: primitive package merged into bson; replace x/bsonx in index.go #4 and Driver v2: Distinct returns a DistinctResult that must be decoded #5 land together in one pull request, worked in that order. Before them, New easymongotest subpackage wrapping mongotest/v2 #7 and Switch the easymongo test suite to easymongotest #8 must land so the test suite no longer depends on the old github.com/tophergopher/mongotest v0.1.0 module (which itself imports easymongo and breaks the moment easymongo's types change). Until mongotest's v2 module is tagged, use a local replace github.com/tophergopher/mongotest/v2 => ../mongotest/v2 in go.mod and say so in the pull request; Toolchain: go 1.27, latest dependencies, tidy, remove replace directives #10 removes it.
• Method is test-driven: write the tests listed under "Tests first", confirm they fail for the expected reason, then implement. Never delete, skip or weaken an existing test to get green; if a test must change because the public API changed (for example primitive.ObjectID to bson.ObjectID), change only the types.
• Driver v2 reference: https://pkg.go.dev/go.mongodb.org/mongo-driver/v2 and the migration guide https://github.com/mongodb/mongo-go-driver/blob/master/docs/migration-2.0.md. Signatures quoted in these issues were checked against v2.9.0.
• Do not add third-party dependencies unless this issue lists them.
• Tracking issue for the whole refactor: Tracking: easymongo refactor (mongo-driver v2, easymongotest helpers, toolchain) #13. The mongotest side is tracked in Tracking: mongotest refactor (stdlib Docker client, driver v1/v2 modules, lighter dependencies) mongotest#48.
• Commit messages: imperative summary line, blank line, body explaining why. Mention this issue number in the pull request description.

Scope

• common_test.go: replace mongotest.NewTestConnection(true) / conn.KillMongoContainer() with easymongotest.Run(t); conn becomes *easymongotest.TestConnection so the embedded *easymongo.Connection methods (Database, D, Ping, MongoURI, DatabaseNames) keep working for the ten test functions (aggregate_test.go, connect_test.go, database_test.go, delete_query_test.go, find_and_query_test.go, find_distinct_test.go, find_query_test.go, index_test.go, insert_query_test.go, update_query_test.go).
• setup(t) / teardown(t) can shrink to conn = easymongotest.Run(t) since Run registers cleanup; keep the helper names so the ten call sites do not change.
• connect_test.go currently imports logrus for a logger fixture; replace with a small test logger implementing easymongo.Logger (also unblocks dropping logrus).
• Remove the direct github.com/tophergopher/mongotest (v1 path) requirement from go.mod.

Implementation details

Current common_test.go (for reference; rewrite it):

var conn *mongotest.TestConnection
func setup(t *testing.T) { conn, err = mongotest.NewTestConnection(true); ...; t.Cleanup(func() { teardown(t) }) }
func teardown(t *testing.T) { conn.KillMongoContainer() }

New version:

var conn *easymongotest.TestConnection
func setup(t *testing.T) { t.Helper(); conn = easymongotest.Run(t) }
func teardown(t *testing.T) { t.Helper() } // kept so call sites compile; Run already registers cleanup

createBatmanArchive(t) and the enemy fixture stay as they are (only the primitive import changes later in #4). connect_test.go builds a logrus logger for ConnectWith(...).Logger(...); replace it with:

type testLogger struct{ t *testing.T }
func (l testLogger) Debugf(f string, a ...interface{}) { l.t.Logf("DEBUG "+f, a...) }
func (l testLogger) Errorf(f string, a ...interface{}) { l.t.Logf("ERROR "+f, a...) }

After the change run go test -race -count=1 ./... && docker ps -a --filter label=mongotest=regression -q | wc -l and confirm the count is 0.

Tests first

This issue is itself the test change. Acceptance is the full suite:

• go test -race ./... passes against Docker with the same ten containers started and removed (verify no mongotest=regression containers remain after the run).

Acceptance

• No *_test.go file imports github.com/tophergopher/mongotest directly; they go through easymongotest.

Depends on: #7.