Support for @CovariantReturnType annotations.

Add new an annotation handler that writes whitelist entries with a modified
signature based on the returnType specified on the annotation.

Also add another handler for the inner annotation, which encapsulates
multiple @CovariantReturnType when it is repeated.

Add unit tests based on the real @CovariantReturnType to verify the logic.

Test: atest class2greylisttest
Bug: 112186571
Change-Id: I4a51d68a48bb06d2360bd348bb9f342053ceb685
5 files changed