Revise SDL 0303 - SDL Audio I/O Manager

[kshala-ford]

This proposal is about integrating a new manager to the sdl_ios library that allows reading audio data from the car microphone and sending audio to the car speaker.

This PR includes the accepted revisions in https://github.com/smartdevicelink/sdl_evolution/issues/1013#issuecomment-682101300 and a minor correction to the state diagram and code. Also includes a note to proposal 0297 to respect the accepted change sending audio in chunks.