Merge changes from topic "nnapi-fl6-android12-vts" into android12-tests-dev

* changes:
  Freeze neuralnetworks AIDL version as v2 for FL6
  Add FL6 spec tests to AIDL VTS.
  Add PACK operation to NNAPI feature level 6.
  AIDL interface changes for NNAPI feature level 6.