getParcelableDescriptor is String16

Switching getParcelableDescriptor to String16:
- consistent w/ interfaces
- can use StaticString16 (no static dirty heap allocation)
- avoid converting these strings utf-8/utf-16

Fixes: 170909836
Test: aidl_integration_test
Change-Id: I197718d630bc008a4872a3e07fb6b6b1af90f128
10 files changed