Adding visionOS support

[eugenehp]

Previous work

• feat(apple): added visionOS support coreaudio-sys#102
• feat(apple): add visionOS support coreaudio-rs#119
• Support visionOS, watchOS, and tvOS coreaudio-sys#103
• Initial changes for adding visionOS support coreaudio-rs#117

Current state

• this repo reuses examples/ios-feedback from coreaudio-rs with few abstractions
• src/host/coreaudio reuses both ios and macos logic from coreaudio-rs

Current work

• @simlay is working on adding tvOS and watchOS support to coreaudio-rs
• I've a version of cpal that works on visionOS
• Released avfaudio

Questions

1. What's a preferred way for reusing iOS example from coreaudio-rs?
2. AVFAudio and AVAudioSession is required to set the playback/record mode on iOS and visionOS devices. Do we abstract it under coreaudio-rs or upstream the changes and include them in cpal too?
3. CI pipeline has to be rebuilt, but not everything can be tested. @simlay suggested to merge all CI builds under apple-tier3 job under one of coreaudio repos. Do we do the same here?
4. Anything I missed?