Post-O. Sketch out CarDiagnosticManager API surface

Provide an implementation of all layers required to plumb CarDiagnosticManager through:
 * CarDiagnosticEvent
 * DiagnosticHalService
 * CarDiagnosticService
 * CarDiagnosticManager

If FutureFeatures are enabled, this is integrated end-to-end enough to run trivial tests of the API

Test: build with TARGET_USES_CAR_FUTURE_FEATURES=true then at a shell runtest -x packages/services/Car/tests/android_car_api_test/ -c android.car.apitest.CarDiagnosticManagerTest
Change-Id: I0f2aafd039d26fec15182dd7029cf8c7995ce85b
18 files changed