Support Chapters in m4a Files

### What problem does this address?

Currently, [chapters in m4a files are not supported in Pocketcasts Android](https://support.pocketcasts.com/article/chapters-android/), likely because [it uses](https://github.com/Automattic/pocket-casts-android/blob/main/modules/services/repositories/src/main/java/au/com/shiftyjelly/pocketcasts/repositories/extensions/MediaMetadataCompatExt.kt) `android.support.v4.media.MediaMetadataCompat` which is an Android provided API.

### What is your proposed solution?

The Android library https://github.com/wseemann/FFmpegMediaMetadataRetriever could be used to get the chapters from m4a files. Here is some sample code: https://github.com/bottiger/SoundWaves/blob/master/app/src/main/java/org/bottiger/podcast/utils/chapter/ChapterUtil.java#L84

### Did you search for existing feature suggestions?

- [X] I have searched for existing feature suggestions.

Start by reading MediaMetadataCompatExt.kt in the repositories module and compare its metadata handling with the ChapterUtil.java example linked in the issue. Evaluate FFmpegMediaMetadataRetriever for extracting chapters from m4a files, then identify the relevant playback and metadata tests. Done means Pocket Casts Android exposes m4a chapter data where chapters are currently unavailable.

Written by the indexing model from the issue text.