Extend NullArgumentForNonNullParameter to match calls to some Immutable* methods and to ArgumentCaptor.forClass.

[copybara-service]

Extend NullArgumentForNonNullParameter to match calls to some Immutable* methods and to ArgumentCaptor.forClass.

• The Immutable* methods of course already throw NullPointerException. And while they're already annotated for nullness, they've been ignored by this checker because there are technical challenges with identifying the nullness of type-variable types loaded from .class files.
• ArgumentCaptor.forClass soon will throw NullPointerException. See Improve vararg handling mockito/mockito#2807 (comment).

To match ArgumentCaptor.forClass, we have to start checking test-only code. But for now, we check such code only for calls to ArgumentCaptor.forClass.

(I suppose that we still don't handle the varargs parameters of the various Immutable* methods, since this entire check skips varargs, in part because varargs are confusing in general (b/232103314) and in part because we can't see annotations on a varargs-element type that is loaded from a .class file. We could make an exception for these methods if we really wanted, but I doubt it's worth it.)