Add voice broadcast slider (#7010)

Riot/Modules/Room/RoomViewController.m

@@ -599,6 +599,7 @@ static CGSize kThreadListBarButtonItemImageSize;
     
     [VoiceMessageMediaServiceProvider.sharedProvider pauseAllServices];
     [VoiceBroadcastRecorderProvider.shared pauseRecording];
+    [VoiceBroadcastPlaybackProvider.shared pausePlaying];
     
     // Stop the loading indicator even if the session is still in progress
     [self stopLoadingUserIndicator];

Riot/Modules/Room/VoiceMessages/VoiceMessageAudioPlayer.swift

@@ -72,6 +72,10 @@ class VoiceMessageAudioPlayer: NSObject {
         return audioPlayer.items()
     }
     
+    var currentUrl: URL? {
+        return (audioPlayer?.currentItem?.asset as? AVURLAsset)?.url
+    }
+    
     private(set) var isStopped = true
     
     deinit {