Load and store URLPreviewViewData in RoomBubbleCellData.

Implement close button and store the action in Core Data. Hide the preview image view when no image is received. Remove line breaks in description text.

Riot/Managers/URLPreviews/ClosedURLPreview.swift

@@ -0,0 +1,22 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+
+extension ClosedURLPreview {
+    // Nothing to extend, however having this file stops Xcode
+    // complaining that it can't find ClosedURLPreview.
+}