Webex SDK: Set default audio output

On Android, we need a method to set the default audio output to the speaker and when a bluetooth headset gets connected, the audio should be played on the headset.

When disconnecting a headseat (during call) the audio should automatically switch back to the speaker.

On iOS we need the same (there is already a method for that, but to play the audio on the headset we use a workaround with the risk that it could not work on future iOS Versions)