refactor: migrate RemoteFeatureFlagController to @metamask/messenger

[cryptodev-2s]

Explanation

This PR migrates RemoteFeatureFlagController to the new @metamask/messenger message bus, 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

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Note

Migrates RemoteFeatureFlagController to the new @metamask/messenger, updates metadata and exports, adjusts tests and TS configs, and documents breaking changes.

• Remote Feature Flag Controller:
  • Migrate from RestrictedMessenger (@metamask/base-controller) to Messenger (@metamask/messenger); update types and constructor to use new messenger.
  • Switch imports to @metamask/base-controller/next.
  • Rename metadata key anonymous to includeInDebugSnapshot (breaking); update tests accordingly.
  • Tidy exports: move RemoteFeatureFlagControllerState type to remote-feature-flag-controller; remove it from remote-feature-flag-controller-types; adjust index.ts exports.
  • Update tests to construct namespaced messengers via @metamask/messenger and new metadata key.
  • Add dependency @metamask/messenger@^0.3.0; update tsconfig references to include packages/messenger.
• Docs/Repo:
  • Update README dependency graph to show remote_feature_flag_controller --> messenger and add eip_7702_internal_rpc_middleware --> controller_utils edge.
  • Update package changelog with breaking changes regarding messenger migration and metadata rename.
  • Refresh lockfile.

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[mcmire]

LGTM!