[clr-interp] Fix more IL_Conformance test issues

[davidwrighton]

• Compare operations between I4 and I need to work
• Storing a floating point value in an array may need conversions
• Storing an I4 into an I with stelem is a supported operation

[Copilot]

Pull Request Overview

This PR fixes several IL conformance test issues in the CoreCLR interpreter by adding implicit type conversions and fixing type handling in various operations.

Key Changes:

• Adds implicit conversions between I4 (int32) and I8 (nint) for comparison operations and array element storage on 64-bit platforms
• Adds implicit floating-point conversions (R4 ↔ R8) for array storage and return statements
• Changes LDLOCA to return InterpTypeI instead of InterpTypeByRef to match existing compiler behavior

[jakobbotsch]

• LDLOCA is specified to return a byref, but the existing compilers treat it as a simple pointer, and we can trivially do it in the interpreter as well. This fixes a bunch of tests.

RyuJIT does not treat LDLOCA as native pointers internally. They are byrefs until they get used in a context that requires a native pointer type (see impBashVarAddrsToI).

I think treating them as native pointers unconditionally will run into other problems... For example, subtracting the address of a local from a byref should result in a native int, but if you treat the address of the local as a native int, then it will result in a byref. Something like:

ref int GetY(ref S s) => ref s.Y;
void Problem()
{
  S s = default;
  GetY(ref s) - ref s; // should be a native int on the stack
}

[davidwrighton]

@jakobbotsch :( Now I have to do a bunch more work. Bummer.

[davidwrighton]

@jakobbotsch I'll tackle the I vs Byref thing in another PR.

[davidwrighton]

/azp run runtime-interpreter

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[davidwrighton]

/azp run runtime-interpreter

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[davidwrighton]

/azp run runtime-interpreter

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