Support MSC4143 RTC Transport endpoint (#3629)

* Use rtc-focus branch of js-sdk

* Update makeTransport to fetch backend transports and validate all transports before response.

* Fix test

* Add test

* Loads more tests

* Add tests for openid errors

* improve comment

* update to develop commit

* Add JWT parsing

* Use JWT

* Cleanup

* fixup tests

* fixup tests

* lint

* lint lint

* Fix `Reconnecting`

src/state/CallViewModel/CallViewModel.test.ts

@@ -1256,7 +1256,9 @@ describe.each([
               rtcSession.membershipStatus = Status.Connected;
             },
             n: () => {
-              rtcSession.membershipStatus = Status.Reconnecting;
+              // NOTE: This was removed in https://github.com/matrix-org/matrix-js-sdk/pull/5103 accidentally.
+              // eslint-disable-next-line @typescript-eslint/no-explicit-any
+              rtcSession.membershipStatus = "Reconnecting" as any;
             },
           });
           schedule(probablyLeftMarbles, {