Bootstrap: spine-cover Locale canonicalize/parse/compose/keywords (#20752)

[PurHur]

Summary

• Restores Pillar 1 Trust after Stdlib: Locale canonicalize/parseLocale/composeLocale/getKeywords (#20738) #20750 landed eight Locale canonicalize/parse/compose/keywords units without compiler_lib_spine_smoke requires.
• Adds alphabetical require_once for the eight files in the spine bundle.

Closes #20752

Test plan

• php script/check-selfhost-spine-coverage-sync.php → OK (spine covers all 5818 inventory files)
• ./script/docker-exec.sh -- bash -lc 'make north-star5-verify-fast' → OK (fast)
• ./script/release-readiness.sh --json → user_release_ready: yes (5/5 quick)

Verification transcript

check-selfhost-spine-coverage-sync: OK (spine covers all 5818 inventory files)
north-star5-verify: OK (fast — use --strict before merging bootstrap/M5 work)
Spine: 5818/5818

release-readiness --json:
  user_release_ready: yes
  bootstrap-inventory: OK 5818/5818
  spine-coverage: ok
  root-readme-sync: ok
  north-star5-fast: ok
  vm-driver-probe: ok

php-src ref: N/A (spine sync only; Locale semantics from #20738/#20750).

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