Element Call video rooms (#9267)

* Add an element_call_url config option

* Add a labs flag for Element Call video rooms

* Add Element Call as another video rooms backend

* Consolidate event power level defaults

* Remember to clean up participantsExpirationTimer

* Fix a code smell

* Test the clean method

* Fix some strict mode errors

* Test that clean still works when there are no state events

* Test auto-approval of Element Call widget capabilities

* Deduplicate some code to placate SonarCloud

* Fix more strict mode errors

* Test that calls disconnect when leaving the room

* Test the get methods of JitsiCall and ElementCall more

* Test Call.ts even more

* Test creation of Element video rooms

* Test that createRoom works for non-video-rooms

* Test Call's get method rather than the methods of derived classes

* Ensure that the clean method is able to preserve devices

* Remove duplicate clean method

* Fix lints

* Fix some strict mode errors in RoomPreviewCard

* Test RoomPreviewCard changes

* Quick and dirty hotfix for the community testing session

* Revert "Quick and dirty hotfix for the community testing session"

This reverts commit 37056514fb.

* Fix the event schema for org.matrix.msc3401.call.member devices

* Remove org.matrix.call_duplicate_session from Element Call capabilities

It's no longer used by Element Call when running as a widget.

* Replace element_call_url with a map

* Make PiPs work for virtual widgets

* Auto-approve room timeline capability

Because Element Call uses this now

* Create a reusable isVideoRoom util

res/css/views/rooms/_RoomPreviewCard.pcss

@@ -64,12 +64,6 @@ limitations under the License.
                 color: $secondary-content;
             }
         }
-
-        /* XXX Remove this when video rooms leave beta */
-        .mx_BetaCard_betaPill {
-            margin-inline-start: auto;
-            align-self: start;
-        }
     }
 
     .mx_RoomPreviewCard_avatar {
@@ -104,6 +98,13 @@ limitations under the License.
                 mask-image: url('$(res)/img/element-icons/call/video-call.svg');
             }
         }
+
+        /* XXX Remove this when video rooms leave beta */
+        .mx_BetaCard_betaPill {
+            position: absolute;
+            inset-block-start: $spacing-32;
+            inset-inline-end: $spacing-24;
+        }
     }
 
     h1.mx_RoomPreviewCard_name {