refactor: migrate AnnouncementController to @metamask/messenger

[mikesposito]

Explanation

This PR migrates the AnnouncementController class to the new @metamask/messenger comm system, as opposed to the one exported from @metamask/base-controller.

References

• Related to Implement messenger delegation #5626

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

---

Note

Migrates AnnouncementController to @metamask/messenger, renames metadata flag, and updates tests/config/docs accordingly.

• Announcement Controller:
  • Migrate to @metamask/messenger Messenger; update imports to @metamask/base-controller/next.
  • Change metadata key from anonymous to includeInDebugSnapshot.
  • Update AnnouncementControllerMessenger type to use Messenger.
• Tests:
  • Replace restricted messenger setup with new Messenger hierarchy; update imports and metadata key usage.
• Package/Config:
  • Add dependency @metamask/messenger@^0.3.0 and TS project references to packages/messenger.
• Docs:
  • Update README.md dependency graph to show announcement_controller --> messenger.
  • Add breaking-change notes to CHANGELOG.md.

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[mcmire]

LGTM!

[mcmire]

LGTM!

[cryptodev-2s]

LGTM!