Start setting the 'c3' mro unambiguously everywhere

Start setting the 'c3' mro unambiguously everywhere

This is a necessary part of the rsrc refactor, which there is no way around.
And yes - it is extremely invasive and dangerous, with very high chance of
fallout. Given the situation there is no other way :/

The implementation itself is rather simple: all we need to do is hook
inject_base (which is called by load_components via several levels of
indirection), and also (as a precaution) we set the mro on anything loaded
via a component-group accessor. This seems to nicely cover pretty much all
of the hierarchy (except ::Storage, but that is another matter/rewrite)

Also move the CAG compat pieces where they belong