[x86/unix] HW instrinsics support

[kvochko]

On x86/unix hardware intrinsics are disabled in the JIT, but enabled in System.Private.CoreLib, which leads to runtime errors. dotnet/coreclr#21164 temporarily solves these errors by disabling intrinsics in S.P.CoreLib, but they should be enabled back when we're certain there are no regressions with intrinsics on that platform.
CC @tannergooding @alpencolt

category:correctness
theme:hardware-intrinsics
skill-level:intermediate
cost:small

[tannergooding]

@parjong commented here that it took too much effort to enable AVX at the time.

If it is just AVX blocking this, then perhaps this could be initially enabled for SSE->SSE4.2 and this bug could explicitly track whatever is blocking AVX...

[tannergooding]

CC. @fiigii, @CarolEidt

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