Android: Add deprecation annotations to VideoRenderer and I420Frame

Bug: webrtc:9181
Change-Id: Ice569c88ce1a2cda6a314f2889c8b64b55cb8c8f
Reviewed-on: https://webrtc-review.googlesource.com/81746
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23543}

sdk/android/api/org/webrtc/VideoRenderer.java

@@ -20,11 +20,15 @@ import org.webrtc.VideoFrame;
  * class also provides a createGui() method for creating a GUI-rendering window
  * on various platforms.
  */
+// Use VideoSink instead.
+@Deprecated
 public class VideoRenderer {
   /**
    * Java version of webrtc::VideoFrame. Frames are only constructed from native code and test
    * code.
    */
+  // Use VideoFrame instead.
+  @Deprecated
   public static class I420Frame {
     public final int width;
     public final int height;