Live location sharing - stop sharing to beacons in rooms you left (#8187)

* remove beacons on membership changes

* add addMembershipToMockedRoom test util

Signed-off-by: Kerry Archibald <kerrya@element.io>

* test remove beacons on membership changes

Signed-off-by: Kerry Archibald <kerrya@element.io>

* removelistener

Signed-off-by: Kerry Archibald <kerrya@element.io>

test/test-utils/index.ts

@@ -2,6 +2,7 @@ export * from './beacon';
 export * from './client';
 export * from './location';
 export * from './platform';
+export * from './room';
 export * from './test-utils';
 // TODO @@TR: Export voice.ts, which currently isn't exported here because it causes all tests to depend on skinning
 export * from './wrappers';