NNAPI: validate that FmqResultDatum padding is 0 -- VTS

FmqResultDatum::OperandInformation has padding that may not be
initialized by an NN HAL service instance. This CL adds a validation
check to ensure that services are not leaking uninitialized data through
this padding region.

Bug: 131356202
Test: mma
Test: atest VtsHalNeuralnetworksV1_2TargetTest
      (for ValidationTest with sample-all)
Test: altered sample-driver to randomly set a padding byte to 1;
      the new validation test successfully failed the test

Change-Id: I6661945392b3fc773493d8f2f306f29b39e09bab