move language filters from QueryFiltersLegacy to QueryFilters

MediaBrowser.Controller/Persistence/IMediaStreamRepository.cs

@@ -21,6 +21,13 @@ public interface IMediaStreamRepository
     /// <returns>IEnumerable{MediaStream}.</returns>
     IReadOnlyList<MediaStream> GetMediaStreams(MediaStreamQuery filter);
 
+    /// <summary>
+    /// Gets all language codes of the provided stream type.
+    /// </summary>
+    /// <param name="mediaStreamType">The type of the media stream.</param>
+    /// <returns>IEnumerable{string}.</returns>
+    IReadOnlyList<string> GetMediaStreamLanguages(MediaStreamType mediaStreamType);
+
     /// <summary>
     /// Saves the media streams.
     /// </summary>