Looks like subclassing classes with resiliently-sized properties works,
as long as the subclass is @_fixed_layout, so let's ensure that's tested.
We don't want @_fixed_layout classes to be a thing though, and we still
can't handle changes to the number of stored properties in a base class,
so a couple of tests are disabled until I land some more patches.
We've already got -enable-resilience and @_fixed_layout to compare
IRGen differences when lowering super_method instructions, so nuke
the -force-resilient-super-dispatch testing flag. While
we're at it, consolidate the super tests a bit.
