🚀 Performance, usability & playback improvements

[alexmercerind]

This PR contains major rewrite of the plugin to improve performance, add new features & more control on playback of audio.

Plugin Changes:

• Now you can listen to playback events using stream (a broadcast stream) inside AudioPlayer. This was a great problem in earlier version as one always needs to trigger UI updates whenever playback progresses, ends etc.
• One of the big problems in earlier version was that there was no way to detect if an audio playback has ended after completion. Resulting in issues like Play songs one after another  #25 & Repeat sound #26. Now audio.isCompleted stores bool if an audio has ended, same can be accessed from stream.
• Added a new Queue class to play audio files sequentially, without having to deal with things like audio.isCompleted etc. manually.
• Added methods to deal with Queue or repeat playback etc.
• Now you can provide any random id while creating new instance of AudioPlayer, this was a big problem earlier as new id had to be consecutive to earlier one.
• Now you can access same instance of AudioPlayer even if you make new constructor, by providing same id.
• Now asset files can be played & loaded into AudioPlayer using load method.
  • AudioSource class has two static methods
    • AudioSource.fromFile to load an audio file.
    • AudioSource.fromAsset to load an audio asset.
• Now audio field stores Audio object, inside the AudioPlayer class & contains following fields to get information about current playback.
  • file: Current loaded File.
  • isPlaying : Whether file is playing.
  • isCompleted: Whether file is ended playing.
    • By default once playback is ended, stop method is called & AudioPlayer is reverted to initial configuration.
  • isStopped: Whether file is loaded.
  • position: Position of current playback in Duration.
  • duration: Duration of current file in Duration.
• Now contructor of AudioPlayer no longer calls async methods, which could result in false assertions.

Native Code Changes:

• Now ma_resource_manager is used from miniaudio_engine with MA_DATA_SOURCE_FLAG_STREAM flag.
  • This will improve general performance during playback, as whole file will not be loaded into memory.
• Structure of code improved & separated into various files & classes.
• Now device handling is present in an entirely separate class AudioDevices.
• Improvements to how methods are identified & called in method channel. flutter_types.hpp improves code readability.
• Other bug-fixes that randomly caused termination after assertion are also fixed to an extent.

Progress on Platforms

• Linux
• Windows
• MacOS (Learn More)

Bringing these changes to Windows will take barely few hours.