Add test to ensure overlays aren't on top of sensor use dialog

This also:
Changes the way camera tests are skipped if none are available
Creates a library to be shared by test apps in this suite

Bug: 199550934
Test: CtsSensorPrivacyTestCases
      run cts -m CtsSensorPrivacyTestCases

Change-Id: I747cc78fe6d9d5dc02d05d23d74438b4684edc15
13 files changed