feat: Add messenger delegate and revoke methods

The methods `delegate` and `revoke` have been added to the Messenger
class. These methods replace the need for the `RestrictedMessenger`.
The `getRestricted` method, and the `RestrictedMessenger` class, have
been removed as obsolete.

See this ADR PR for details: MetaMask/decisions#53

Author: Gudahtt

packages/messenger/CHANGELOG.md

@@ -10,5 +10,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Migrate `Messenger` class from `@metamask/base-controller` package ([#6127](https://github.com/MetaMask/core/pull/6127))
+- Add `delegate` and `revoke` methods ([#6132](https://github.com/MetaMask/core/pull/6132))
+  - These allow delegating or revoking capabilities (actions or events) from one `Messenger` instance to another.
+  - This allows passing capabilities through chains of messengers of arbitrary length
+  - See this ADR for details: https://github.com/MetaMask/decisions/blob/main/decisions/core/0012-messenger-delegation.md
+
+### Changed
+
+- **BREAKING:** Add `Namespace` type parameter and required `namespace` constructor parameter ([#6132](https://github.com/MetaMask/core/pull/6132))
+  - All published events and registered actions should fall under the given namespace. Typically the namespace is the controller or service name. This is the equivalent to the `Namespace` parameter from the old `RestrictedMessenger` class.
+- **BREAKING:** Remove `RestrictedMessenger` class ([#6132](https://github.com/MetaMask/core/pull/6132))
+  - Existing `RestrictedMessenger` instances should be replaced with a `Messenger`. We can now use the same class everywhere, passing capabilities using `delegate`.
+  - See this ADR for details: https://github.com/MetaMask/decisions/blob/main/decisions/core/0012-messenger-delegation.md
 
 [Unreleased]: https://github.com/MetaMask/core/