Investigate need for non-strict method match in JavacTypes

JDK-8278373 fixes a bug in JavacTypes method lookup with an improved but compatible behavior. The behavior showed up various bugs in the generated JDK API docs for older versions of javadoc.

We should investigate whether the older non-strict behavior is still needed and/or desirable, perhaps by disabling it and building the JDK API docs. If it is needed, maybe the behavior could be opt-in for a transition period until we can remove it.

Related: javadoc could also give a warning if a non-exact match is found. The warning should come from javadoc, and not JavacTypes, because JavacTypes does not have access to the right reporting mechanisms, and anyway, we do not expect diagnostics (even warnings) from impls of Elements and Types.