Refactor AudioActivity to Controller and ViewModel architecture

- Refactored AudioActivity to use Compose UI, AudioViewModel, and AudioController.
- Managed AudioRecord, AudioTrack, and ProjectedDeviceController
  lifecycles in Controller.
- Released audio resources cleanly on close to avoid background audio
  leakage.

Test: ./gradlew :xr:projected:integration-tests:testapp:lintDebug
Test: ./gradlew :xr:projected:integration-tests:testapp:assembleDebug
Relnote: N/A
Change-Id: I9bb25ed91cef97b9a38152eb87a9fb5d6effed77