Add Quality of Service to NNAPI HAL

This CL makes the following changes:
* introduces a new Priority enum
* extends ErrorStatus with new error codes
* adds "supportsDeadline" method to IDevice
* adds priority and deadline arguments to IDevice::prepareModel*
* adds deadline argument to IPreparedModel::execute*
* updates IExecutionCallback with new ErrorStatus
* updates current.txt accordingly

Bug: 136739795
Bug: 142902514
Bug: 145300530
Test: mma
Change-Id: Iaa7877bde1f463635b8bbdb4e8a001d7b79b9c65