An alternate approach to what was attempted in #3962 (and dotnet/coreclr#12420), this time leveraging preexisting infrastructure in RyuJIT built for accessing RVA static fields. This is limited to non-GC statics, since that's what RyuJIT has.

It feels a bit more natural to how JitInterface is structured (e.g. RyuJIT is calling initClass to eliminate the need to do the cctor check in some cases). If this is something we would want to take further, the next steps would be:

1. Update initClass to allow generating the inline cctor check (we currently call the ReadyToRun helper to get non-GC static base - this change doesn't affect that).
2. Change CORINFO_FIELD_INFO - replace CORINFO_CONST_LOOKUP fieldLookup with CORINFO_LOOKUP fieldLookup so that we can also do this from shared code.
3. Some updates to handle GC statics and thread statics that I haven't thought about too much yet.

I don't have plans to do the next steps anytime soon though.

The changes to the generated code look like this:

internal class Program
{
    static int X;
    static int Y;

    private static int Main()
    {
        return X + Y;
    }
}

Before:

call        __GetNonGCStaticBase_repro_Program (07FF65ADE2FCCh)  
mov         edx,dword ptr [rax]  
add         edx,dword ptr [rax+4]  
mov         eax,edx  

After:

mov         eax,dword ptr [repro_Program::__NONGCSTATICS (07FF66540BBD8h)]  
add         eax,dword ptr [repro_Program::__NONGCSTATICS+4h (07FF66540BBDCh)]