Fixes #978 - Message forwarding support

* Add support for message forwarding

* Move the TimelineProvider within the RoomProxy to avoid it going out of sync and have it automatically register for timeline updates on init

* Implement single selection form button style for message forwarding

* Add searching and filter out the source room from the list

* Fixed emoji screen initial search bar height

* Add view models tests

* Add changelog

* Update strings

* Tweaks following code review

ElementX/Sources/Other/AvatarSize.swift

@@ -76,12 +76,15 @@ enum UserAvatarSizeOnScreen {
 enum RoomAvatarSizeOnScreen {
     case timeline
     case home
+    case messageForwarding
     case details
 
     var value: CGFloat {
         switch self {
         case .timeline:
             return 32
+        case .messageForwarding:
+            return 36
         case .home:
             return 52
         case .details: