Allow changing of output device

[Danielku15]

See #634 (comment)

alphaTab should expose an API to allow changing the output device.

• Web
  • Requesting permission: await navigator.mediaDevices.getUserMedia({ audio: true });
  • Listing devices: (await navigator.mediaDevices.enumerateDevices()).filter(device => device.kind === 'audiooutput')
  • DeviceID: string
  • Setting initial output: new AudioContext({sinkID: device.deviceId})
  • Changing output dynamically: await audioContext.setSinkId(device.deviceId)
• .net
  • Requesting permission: not needed
  • Listing devices: NAudio.Wave.DirectSoundOut.Devices
  • DeviceID: System.Guid
  • Setting initial output: new NAudio.Wave.DirectSoundOut(deviceId, latency)
  • Changing output dynamically: Not available, would require recreation DirectSoundOut
• Android
  • Requesting permission:
  • Listing devices: ((AudioManager) context.getSystemService(Context.AUDIO_SERVICE)).getDevices(AudioManager.GET_DEVICES_OUTPUTS)
  • DeviceID: AudioDeviceInfo
    
  • Setting initial output: audioTrack.setPreferredDevice()
  • Changing output dynamically: audioTrack.setPreferredDevice()

alphaTab design:

• alphaTab should provide its own abstraction for the output devices to provide a unified experience across platforms.
• Due to the dynamic nature of first enumerating devices and then selecting one, the output device cannot be part of the Settings
• Low Level API:
  • The ISynthOutput initializes with the default device
  • A new interface ISynthOutputDevice { ... } will represent the platform specific devices.
  • A new interface ISynthOutput { enumerateDevices(): Promise<ISynthOutputDevice> method enumerate and list the devices (it also will request permissions if needed).
  • A new interface ISynthOutput { setOutputDevice(device: ISynthOutputDevice|null): Promise<void> method will change the output device. Null restores the default output device.
  • A new interface ISynthOutput { getOutputDevice(): Promise<ISynthOutputDevice|null> method try to determine the current output device.
  • Multiple ISynthOutputDevice instances for the same output device might be created across API calls.
• High level API:
  • Re-Expose enumerateDevices on AlphaTabApiBase
  • Re-Expose setOutputDevice on AlphaTabApiBase
  • Re-Expose getOutputDevice on AlphaTabApiBase