Enable NN VTS and utility code to use lazy services

This CL enables VtsHalNeuralnetworksTargetTest to use lazy services by
changing from AServiceManager_getService (which will return nullptr for
the service if the service is not able to be loaded within a short
amount of time) to AServiceManager_waitForService (which will wait for a
longer time, allowing lazy services to start up).

Similarly, the utility code is changed from using
AServiceManager_getService to AServiceManager_waitForService where
possible.

This CL also introduces an "InvalidDevice" utility class to the
nnapi/hal/aidl utility code. InvalidDevices are minimal devices that
support no functionality but are still able to pass VTS tests.

Bug: 170696939
Test: mma
Test: VtsHalNeuralnetworksTargetTest
Change-Id: I4f806b104ef6af863ec55c2c3f2a2dd1f72b9633