Make EncoderBitrateProvider and implementations package private.

There is no API to allow applications to use these currently. Until
that exists, these classes do not need to be public.

PiperOrigin-RevId: 500792401

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/DeviceMappedEncoderBitrateProvider.java

@@ -20,7 +20,7 @@ import android.os.Build;
 import com.google.android.exoplayer2.util.Util;
 
 /** Provides encoder bitrates that should target 0.95 SSIM or higher, accounting for device used. */
-public class DeviceMappedEncoderBitrateProvider implements EncoderBitrateProvider {
+/* package */ class DeviceMappedEncoderBitrateProvider implements EncoderBitrateProvider {
 
   @Override
   public int getBitrate(String encoderName, int width, int height, float frameRate) {

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/EncoderBitrateProvider.java

@@ -19,7 +19,7 @@ package com.google.android.exoplayer2.transformer;
 import android.media.MediaCodecInfo;
 
 /** Provides bitrates for encoders to use as a target. */
-public interface EncoderBitrateProvider {
+/* package */ interface EncoderBitrateProvider {
 
   /**
    * Returns a recommended bitrate that the encoder should target.