Refactor encryption information.

We had lots of enums and booleans to describe the encryption situation.
Now we only use the `EncryptionSystem` "enum" which contains the
additional information like sharedKey. (and we don't use the isRoomE2EE
function that is somewhat confusing since it checks `return widget ===
null && !room.getCanonicalAlias();` which is only indirectly related to
e2ee)

Signed-off-by: Timo K <toger5@hotmail.de>

src/widget.ts

@@ -122,6 +122,7 @@ export const widget = ((): WidgetHelpers | null => {
       ];
       const receiveState = [
         { eventType: EventType.RoomMember },
+        { eventType: EventType.RoomEncryption },
         { eventType: EventType.GroupCallPrefix },
         { eventType: EventType.GroupCallMemberPrefix },
       ];