MatrixRTC: Implement expiry logic for CallMembership and additional test coverage (#4587)
* remove all legacy call related code and adjust tests.
We actually had a bit of tests just for legacy and not for session events. All those tests got ported over so we do not remove any tests.
* dont adjust tests but remove legacy tests
* Remove deprecated CallMembership.getLocalExpiry()
* Remove references to legacy in test case names
* Clean up SessionMembershipData tsdoc
* Remove CallMembership.expires
* Use correct expire duration.
* make expiration methods not return optional values and update docstring
* add docs to `SessionMembershipData`
* Add new tests for session type member events that before only existed for legacy member events.
This reverts commit 795a3cffb61d672941c49e8139eb1d7b15c87d73.
* remove code we do not need yet.
* Cleanup
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Co-authored-by: Hugh Nimmo-Smith <hughns@matrix.org>