Add HLS precaching support for Android

[alexgrusu]

This work introduces support for scenarios where we want to precache data and play it directly from the local cache.

To test playback from cache, you have to make this change:

class HlsAudioSource extends UriAudioSource {
  HlsAudioSource(Uri uri,
      {Map<String, String>? headers, dynamic tag, Duration? duration})
      : super(uri, headers: headers, tag: tag, duration: duration);

  @override
  AudioSourceMessage _toMessage() => HlsAudioSourceMessage(
        id: _id,
        // Previously: uri: _effectiveUri.toString(),
        uri: uri.toString(), // Now uses the original (potentially local) URI
        headers: _mergedHeaders,
        tag: tag,
      );
}

With this change, we can use a local file URI when needed, enabling playback from a locally cached file instead of always fetching from a remote URL.

I'm considering a cleaner way to bypass the local URL logic when needed, so suggestions or alternative approaches are welcome!

I'm moving on to implement similar support on the iOS side next.

Please let me know if you find this useful or have any feedback, especially regarding the local URL bypass or improvements for broader platform support.