Add headers for the type parameters in all generic types

Simplifying the AddHeaders function for cpp backend.
Once we are finished handling a type, we will return.
If this is an unexpected or unhandled type, we will abort instead of
just returning.

Test: atest aidl_integration_test aidl_unittests
Bug: 142326204
Change-Id: I2559d4bf99f8b2f4173ca6bc13a3c0fa085bdf74
4 files changed