Add a warning about device specific tunneling issues

There has been many issue recently about tunneling
that have no obvious solutions and we don't have the
bandwidth to dive into the platform root cause.

- https://github.com/google/ExoPlayer/issues/9661
- https://github.com/google/ExoPlayer/issues/9133
- https://github.com/google/ExoPlayer/issues/9317
- https://github.com/google/ExoPlayer/issues/9502

PiperOrigin-RevId: 410834262

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/trackselection/DefaultTrackSelector.java

@@ -572,6 +572,13 @@ public class DefaultTrackSelector extends MappingTrackSelector {
      * Sets whether to enable tunneling if possible. Tunneling will only be enabled if it's
      * supported by the audio and video renderers for the selected tracks.
      *
+     * <p>Tunneling is known to have many device specific issues and limitations. Manual testing is
+     * strongly recomended to check that the media plays correctly when this option is enabled. See
+     * [#9661](https://github.com/google/ExoPlayer/issues/9661),
+     * [#9133](https://github.com/google/ExoPlayer/issues/9133),
+     * [#9317](https://github.com/google/ExoPlayer/issues/9317),
+     * [#9502](https://github.com/google/ExoPlayer/issues/9502).
+     *
      * @param tunnelingEnabled Whether to enable tunneling if possible.
      * @return This builder.
      */