Add the inviter to JoinRoomScreen when it's an invite. (#3093)

* Add inviter property to RoomProxyProtocol.

* Extract the room cell inviter label into it's own view.

* Use the new RoomInviterLabel in the JoinRoomScreen.

* Fix bug with invite to a public room.

ElementX/Sources/Services/Room/RoomProxy.swift

@@ -64,6 +64,12 @@ class RoomProxy: RoomProxyProtocol {
         room.membership()
     }
     
+    var inviter: RoomMemberProxyProtocol? {
+        get async {
+            await (try? roomListItem.roomInfo().inviter).map(RoomMemberProxy.init)
+        }
+    }
+    
     var isDirect: Bool {
         room.isDirect()
     }

ElementX/Sources/Services/Room/RoomProxyProtocol.swift

@@ -40,6 +40,7 @@ protocol RoomProxyProtocol {
     var isFavourite: Bool { get async }
     var pinnedEventIDs: [String] { get async }
     var membership: Membership { get }
+    var inviter: RoomMemberProxyProtocol? { get async }
     var hasOngoingCall: Bool { get }
     var canonicalAlias: String? { get }
     var ownUserID: String { get }