Evaluate JIT_MemCpy without overlap check

[helloguo]

The current implementation of JIT_MemCpy on x64 Windows checks for address overlap and different paths are taken depending on result. However, ECMA-335 mentions "The behavior of cpblk is unspecified if the source and destination areas overlap". An optimized version without overlap check may be worth evaluating and implementing. dotnet/coreclr#7198

category:cq
theme:helpers
skill-level:expert
cost:medium

[TIHan]

Comment regarding the overlapping buffers:

        ; Use memmove to handle overlapping buffers for better
        ; compatibility with .NET Framework. Needing to handle
        ; overlapping buffers in cpblk is undefined by the spec.

It might be worth evaluating? Hard to tell, but keeping this as future.

[EgorBo]

Closed by #98623

[EgorBo]

Ah, sorry, it's a different issue. Although, I don't think we'll remove the overlap check