Add membershipID to call memberships (#3745)

* Add membershipID to call memberships

This allows us to recognise easily when a membership is from some
previous sessions rather than our own and therefore ignore it
(see comment for more).

This was causing us to see existing, expired membership events and
bump the expiry on them rather than send a new membership. This might
have been okay if we bumped them enough to actually make them un-expired,
but it's a fresh session so semanticly we want to post a fresh membership
rather than resurrecting a previous, expired membership.

* Fix test types

* Fix tests

* Make test coverage happy

---------

Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

spec/unit/matrixrtc/MatrixRTCSessionManager.spec.ts

@@ -26,6 +26,7 @@ const membershipTemplate: CallMembershipData = {
     application: "m.call",
     device_id: "AAAAAAA",
     expires: 60 * 60 * 1000,
+    membershipID: "bloop",
 };
 
 describe("MatrixRTCSessionManager", () => {