refactor(databars): split blocks into Blocks/ files

[Caedis]

What does this PR do?

One file per block type
Shared helpers in Blocks/Shared.lua exposed via ns.BlockKit.
Block code moved verbatim, no behavior change.

How was it tested?

Tested in Forever. Loaded in with 0 issues and 0 changes.

Checklist

• [N/A] New settings default OFF (no behavior change without opt-in)
• [N/A] Zero cost while disabled: no events registered, no polling, no hooks doing work, no frames built
• [N/A] Cheap while enabled: event-driven (no polling, no timer-based logic, no per-frame allocations)
• [N/A] No writes onto Blizzard-owned frames (weak-table pattern used); HookScript/hooksecurefunc only, never SetScript on Blizzard frames
• Tested in-game on live; no version gates or pre-Midnight APIs added

[Caedis]

May cause conflicts with other PRs that touch the _Blocks.lua file