MatrixRTCSessionManager own membership management makes requests to homeserver to frequently

[hughns]

During testing we have noticed a number of issues with how matrix-js-sdk is managing the m.call.member room state events for the local user.

Specifically the MatrixRTCSessionManager is making requests to the homeserver more frequently than expected. This can cause issues on large calls.

Whilst the behaviour of the matrix-js-sdk hasn't changed, these issues became more apparent when #2701 landed as it made the visual representation dependent on the room state not the SFU participants.

The plan it to simplify the code and tighten up the implementation.

Items that are part of this:

• Remove support for "legacy" MSC3898 group calling in MatrixRTCSession and CallMembership matrix-org/matrix-js-sdk#4583
• MatrixRTC: Implement expiry logic for CallMembership and additional test coverage matrix-org/matrix-js-sdk#4587
• MatrixRTC: move MatrixRTCSession logic into LocalMembershipManager matrix-org/matrix-js-sdk#4608
• MatrixRTC: refactor MatrixRTCSession MemberManager API matrix-org/matrix-js-sdk#4610
• MatrixRTC: additional TS docs for IMembershipManager interface matrix-org/matrix-js-sdk#4613
• MatrixRTC: refactor MatrixRTCSession media encryption key logic into EncryptionManager matrix-org/matrix-js-sdk#4612