Review backout logic in the type loader

[MichalStrehovsky]

#71524 (comment)

Depending on our future thoughts about universal shared code and JIT/interpreter support, we might want to consider bringing back the pre-USG version of the type loader that was a lot simpler and easier to work with. Might be cheaper to restore that and tweak it than to simplify the existing System.Private.TypeLoader logic that kind of organically outgrew its original purpose.