[ClangFormat] Fix formatting bugs. (#76245)

1. There are multiple calls to addFakeParenthesis; move the guard to not
   assign fake parenthesis into the function to make sure we cover all
   calls.
2. MustBreakBefore can be set on a token in two cases: either during
   unwrapped line parsing, or later, during token annotation. We must
   keep the latter, but reset the former.
3. Added a test to document that the intended behavior of preferring not
   to break between a return type and a function identifier.
   For example, with MOCK_METHOD(r, n, a)=r n a, the code
   MOCK_METHOD(void, f, (int a, int b)) should prefer the same breaks as
   the expanded void f(int a, int b).