[runtime] Avoid caching member_ref tokens of dynamic images. Fixes #16096

SRE encodes references to self-instantiated generic types in a different way
that regular code.

This is required as there's no clear way to differentiate between an open type
and a self-instantiated type when using System.Type.

Given that restriction, code that deals with loading such methods must take
special case and not cache then as the context under generic sharing will not
be used - so it would be seen as cacheable.

When using regular instantiation the same method lookup will require the context
to be used but will hit the cache before.

This is another problem of passing the instantiation context around. It messes
up with way too much stuff.
[bcl] Add regression test for bxc #16096.