Make audio track min buffer size configurable.

Move the code in its own class as DefaultAudioTrack
is getting very big. It also help for testability.

The new class is easily configurable and highly tested.
Manual test was used to catch any regression.

https://github.com/google/ExoPlayer/issues/8891

PiperOrigin-RevId: 424602011

RELEASENOTES.md

@@ -53,6 +53,9 @@
         constructors.
     *   Change `AudioCapabilities` APIs to require passing explicitly
         `AudioCapabilities.DEFAULT_AUDIO_CAPABILITIES` instead of `null`.
+    *   Allow customization of the `AudioTrack` buffer size calculation by
+        injecting an `AudioTrackBufferSizeProvider` to `DefaultAudioSink`.
+        ([#8891](https://github.com/google/ExoPlayer/issues/8891)).
 *   Extractors:
     *   Fix inconsistency with spec in H.265 SPS nal units parsing
         ([#9719](https://github.com/google/ExoPlayer/issues/9719)).