Refactoring and tidy up.

Make the preview manager a singleton (passing in the MXSession to functions). Fix tests.

PreviewManager → URLPreviewManager
URLPreviewViewData → URLPreviewData
URLPreviewCache → URLPreviewStore

Riot/Modules/Room/CellData/RoomBubbleCellData.h

@@ -15,7 +15,7 @@
  */
 
 #import <MatrixKit/MatrixKit.h>
-@class URLPreviewViewData;
+@class URLPreviewData;
 
 extern NSString *const URLPreviewDidUpdateNotification;
 
@@ -84,7 +84,7 @@ typedef NS_ENUM(NSInteger, RoomBubbleCellDataTag)
 /**
  A link if the textMessage contains one, otherwise nil.
  */
-@property (nonatomic) URLPreviewViewData *urlPreviewData;
+@property (nonatomic) URLPreviewData *urlPreviewData;
 
 /**
  MXKeyVerification object associated to key verification event when using key verification by direct message.

Riot/Modules/Room/CellData/RoomBubbleCellData.m

@@ -1071,7 +1071,7 @@ NSString *const URLPreviewDidUpdateNotification = @"URLPreviewDidUpdateNotificat
     }
     
     // Check that the preview hasn't been dismissed already.
-    if ([LegacyAppDelegate.theDelegate.previewManager hasClosedPreviewFrom:lastComponent.event])
+    if ([URLPreviewManager.shared hasClosedPreviewFrom:lastComponent.event])
     {
         return;
     }
@@ -1079,7 +1079,10 @@ NSString *const URLPreviewDidUpdateNotification = @"URLPreviewDidUpdateNotificat
     // Set the preview data.
     MXWeakify(self);
     
-    [LegacyAppDelegate.theDelegate.previewManager previewFor:lastComponent.link and:lastComponent.event success:^(URLPreviewViewData * _Nonnull urlPreviewData) {
+    [URLPreviewManager.shared previewFor:lastComponent.link
+                                     and:lastComponent.event
+                                    with:self.mxSession
+                                 success:^(URLPreviewData * _Nonnull urlPreviewData) {
         MXStrongifyAndReturnIfNil(self);
         
         // Update the preview data and send a notification for refresh