feat(android)!: configurable SoundPool and AudioManager.mode

[Gustl22]

• feat(android): configurable SoundPool in LOW_LATENCY mode
• fix(android): apply global AudioContext to MediaPlayer
• feat(android): add AudioMode to AudioContextAndroid
• feat(android): set AudioManager.mode and AudioManager.isSpeakerphoneOn on setGlobalAudioContext
• docs: add missing docs for audio_context_config library
• docs: add docs on how to set platform-specific audio context

Description

SoundPool could not be configured with AudioContext attributes. This Merge Request adds the functionality to also configure playing sources in LOW_LATENCY mode.

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs:, chore: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation and added dartdoc comments with ///, where necessary.
• I have updated/added relevant examples in example.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

Migration instructions

If you create an AudioPlayer in LOW_LATENCY mode, it's presets are not the same as before as they are taken from the AudioContext now. Nether the less you can set them via:

final audioContext = const AudioContext(
  android: AudioContextAndroid(
    usageType: AndroidUsageType.game,
  ),
),

Set context globally, before creating a player:

AudioPlayer.global.setGlobalAudioContext(audioContext);
final player = AudioPlayer()..setPlayerMode(PlayerMode.lowLatency);

Set context for an existing single player:

player.setPlayerMode(PlayerMode.lowLatency)
player.setAudioContext(audioContext );

Related Issues

Closes #1240
Closes #135

Related:
#1202
#1321
#934

[Gustl22]

Consider adding the bullets in the PR description, when squashing.