Fix ClassCastException in RemoveTimesZeroAndOne

[timtebeek]

Summary

• Fixes RemoveTimesZeroAndOne - class J$Identifier cannot be cast to class J$MethodInvocation #968
• Added instanceof J.MethodInvocation check before casting the second argument of verify() in RemoveTimesZeroAndOne, preventing a ClassCastException when the argument is an identifier (e.g., a VerificationMode variable) rather than a times() call
• Added test case for verify(obj, verificationMode) where verificationMode is a variable

Test plan

• New test retainVerificationModeIdentifier passes
• All existing tests still pass