refactor: migrate SignatureController to @metamask/messenger

[cryptodev-2s]

Explanation

This PR migrates SignatureController 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 SignatureController to the new @metamask/messenger API, renames the anonymous metadata flag, and updates tests and configs accordingly.

• Signature Controller:
  • Migrate from RestrictedMessenger (via @metamask/base-controller) to Messenger from @metamask/messenger; replace messagingSystem calls with messenger.call for keyring, approval, logging, network, and accounts actions.
  • Import BaseController (and types) from @metamask/base-controller/next.
  • Rename state metadata key anonymous to includeInDebugSnapshot and update stateMetadata accordingly.
• Tests:
  • Update to use @metamask/base-controller/next deriveStateFromMetadata and mock SignatureControllerMessenger with messenger.call routing.
  • Adjust assertions for renamed metadata flag.
• Package/Config:
  • Add dependency @metamask/messenger and reference it in tsconfig project references.
  • Update README dependency graph to show signature_controller --> messenger and add eip_7702_internal_rpc_middleware link.
• Changelog:
  • Note BREAKING changes: new Messenger type and metadata flag rename.

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[mcmire]

LGTM!