aidl: tests: add PersistableBundle integration tests

Add integration tests for PersistableBundle. Since the aidl
generator currently does not support out params for
PersistableBundles (b/25998882), we do not test for this.

Also:
- Rename ConfirmParcelables() to ConfirmSimpleParcelables().
  This makes the addition of ConfirmPersistableBundles() less
  confusing, since PersistableBundles are also Parcelables.
- Minor formatting changes in aidl_test_service.cpp.

BUG: 25815410
Change-Id: Ib20f6ecf47dec556929b3fe30e45aa7e410d9054
TEST: aidl builds successfully.
TEST: integration-test.py passes.
7 files changed