[duplicated subtitle] Fix the issue of duplicated subtitles on the screen display (with ExoPlayer module).

- Replace StreamInfo.getSubtitles() with AppStreamInfo.loadNormalizedSubtitles()
  to download TTML subtitles and deduplicate them.
- Note: each module calling subtitle normalization will perform network download
  independently. AppStreamInfo cannot be shared across modules like StreamInfo.

Author: TransZAllen

app/src/main/java/org/schabi/newpipe/player/resolver/VideoPlaybackResolver.java

@@ -21,6 +21,7 @@
 import org.schabi.newpipe.player.helper.PlayerHelper;
 import org.schabi.newpipe.player.mediaitem.MediaItemTag;
 import org.schabi.newpipe.player.mediaitem.StreamInfoTag;
+import org.schabi.newpipe.streams.AppStreamInfo;
 import org.schabi.newpipe.util.ListHelper;
 
 import java.util.ArrayList;
@@ -136,7 +137,8 @@ public MediaSource resolve(@NonNull final StreamInfo info) {
         // Below are auxiliary media sources
 
         // Create subtitle sources
-        final List<SubtitlesStream> subtitlesStreams = info.getSubtitles();
+        final AppStreamInfo appInfo = AppStreamInfo.from(info);
+        final List<SubtitlesStream> subtitlesStreams = appInfo.loadNormalizedSubtitles();
         if (subtitlesStreams != null) {
             // Torrent and non URL subtitles are not supported by ExoPlayer
             final List<SubtitlesStream> nonTorrentAndUrlStreams = getUrlAndNonTorrentStreams(