android Bluetooth lag, device change event, iOS earpeice

[mouEsam]

This PR contains:

• Fix for device change handler being overridden when another flutter engine get registered.
• Switching twilio audioswitch back to the old fork to solve an issue where Bluetooth devices cause the device to lag and hang very hard on android 11-13 (Not tested on Android 10).
• Switching the audio mode to VoiceChat when speaker is not activated on iOS

[berger89]

@mouEsam
can you please fix the failed Build for Flutter Android (pull_request) job?

[mouEsam]

@berger89 It seems that GitHub actions can't find the specified fork of audioSwitch, however i build and run the example just fine so it might be a missing ssh configuration on the side of the owner of this branch. Nevertheless, I'll look for an alternative fork available through a published repository that solves the Bluetooth lag problem.

[mouEsam]

All tests pass. @berger89
Would you kindly review this PR? the multiple engines issue is very critical.

[berger89]

@cloudwebrtc
looks good to me. Can you confirm this and make a release for it?