Don't use erased type for diagnostic output

[aosen-xiong]

This PR improves diagnostic output for method invocation mismatches by using exact type arguments instead of RAW types. It also added a test case for error reporting in method invocation mismatches.

Seperate from #793

[wmdietl]

Thanks!
A changelog entry/closed issue note would be good.

[wmdietl]

Thanks for the updates. Please think a bit more about what this code should do.

[aosen-xiong]

@wmdietl I agree the logic does not make sense. We had #793 to make the logic consistent, and it checks for type argument annotations on the method receiver.

So, there are two things that need to be changed in this logic.

1. the diagnostic output
2. the subtype checking logic

Do we still want two separate PRs? Or we can use #793 to do both.

[wmdietl]

Suggested change

	AnnotatedTypeMirror methodReceiver = method.getReceiverType();
	AnnotatedTypeMirror erasedMethodReceiver = methodReceiver.getErased();

How about introducing this extra variable instead of calling the same method four times?

[aosen-xiong]

Thanks for the suggestion. I directly committed locally and made this suggestion outdated. Sorry about that.

[wmdietl]

Thanks, looks good.