Add canonical types adapters for NNAPI AIDL interface

Also:
* Add missing AIDL<->CT conversions
* Add AIDL-specific info to neuralnetworks/utils/README.md
* Add mock classes and tests AIDL adapters

Bug: 179015258
Test: neuralnetworks_utils_hal_test
Change-Id: Ifa98fadd46dca5dbf9b3ceb4da811aa8da45b6e4