Audio: Add VTS tests for invalid enum-strings, Part 1

Add tests that try passing invalid enum-string values to HAL
methods taking enum-strings. Fix issues found in the default
wrapper.

Interface updates:

- Update AudioConfig structure to indicate whether
  AudioOffloadInfo is specified.

- Add return value to IStreamIn.updateSinkMetadata
  and IStreamOut.updateSourceMetadata to provide indication
  of invalid arguments.

- Specify the behavior of IDevice.open{Input|Output}Stream
  in the case of invalid arguments vs. rejected config.

Bug: 142480271
Test: atest VtsHalAudioV6_0TargetTest
Test: atest VtsHalAudioV7_0TargetTest
      with side-loaded V7 default wrapper
Change-Id: I6bd7be3869cc7a8d5d00506565bbf0b3a050b630