refactor: migrate KeyringController to @metamask/messenger

[mikesposito]

Explanation

This PR migrates the KeyringController controller 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 KeyringController to @metamask/messenger, updates metadata flag and tests, and adds new messenger dependency/config refs.

• Keyring Controller:
  • Migrates messaging from RestrictedMessenger (@metamask/base-controller) to Messenger (@metamask/messenger); switches to BaseController from @metamask/base-controller/next.
  • Replaces messagingSystem.publish/registerActionHandler with messenger.publish/registerActionHandler and updates KeyringControllerMessenger type.
  • Renames metadata key anonymous to includeInDebugSnapshot and updates calls to deriveStateFromMetadata.
• Tests:
  • Refactors to build a root Messenger and namespaced controller messenger; updates expectations for metadata snapshots and messaging APIs.
• Repo/Config:
  • Adds dependency @metamask/messenger and TypeScript project references; updates README dependency graph to show keyring_controller --> messenger and eip_7702_internal_rpc_middleware --> controller_utils.
• Changelog:
  • Notes BREAKING changes: switch to @metamask/messenger and metadata flag rename.

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[Gudahtt]

Look good!

[mcmire]

LGTM!

[cryptodev-2s]

LGTM!