Fix framerate based bitrate adjuster.

Fixes target bitrate calculation for framerate based adjuster. Adds new
API to bitrate adjuster - getCodecConfigFramerate() - that returns the
FPS that should be passed to MediaCodec on initialization.

Bug: b/73741487, cl/186656928
Change-Id: Ia4a5e99d302de67fbee0c132ab8e9392bc205b44
Reviewed-on: https://webrtc-review.googlesource.com/65162
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22716}

sdk/android/src/java/org/webrtc/BaseBitrateAdjuster.java

@@ -32,7 +32,7 @@ class BaseBitrateAdjuster implements BitrateAdjuster {
   }
 
   @Override
-  public int getAdjustedFramerate() {
+  public int getCodecConfigFramerate() {
     return targetFps;
   }
 }