Merge changes from topic "fix_headset_test_flakiness" into main

* changes:
  HeadsetTest: Use injected test looper and Truth
  HeadsetTest: cleanup invalid check and comments
  HeadsetTest: remove unused Intent
  HeadsetTest: Unify test to use doReturn
  HeadsetTest: localAdapter & not depend on intent
  HeadsetTest: Delete un-necessary reflection
  HeadsetTest: Re-order variable
  HeadsetTest: apply format