MatrixRTC: Refactor | Introduce a new Encryption manager (used with experimental to device transport)

[BillCarsonFr]

Add a new simplified EncryptionManager that will rotate the key for any membership change (join or leave or same)

There is no specific experimental flag to use it, it will use it for to device transport

Checklist

• [ ] Tests written for new code (and old code if feasible).
• [ ] New or updated public/exported symbols have accurate TSDoc documentation.
• [ ] Linter and other CI checks pass.
• [ ] Sign-off given on the changes (see CONTRIBUTING.md).