It's currently very unclear whether CORINFO_FLG_CONTAINS_GC_PTR works for all the kinds of refs and pointers we care about. My initial scan of the codebase suggests it might not (thanks to jan kotas for pointing this out).

I need to verify that it works for everything we care about, and if it doesn't, update the interpreter compiler to not rely on it. Currently some parts of it do and some parts of the compiler use getClassGCLayout instead (which I believe does work how we want, but is more expensive.)