[S390X] Add simd fallback support for unsupported s390x architectures

[saitama951]

Vector facility was introduced in the z13, which majorly introduces vector int/short/long/double variants of the vector instructions. with the release of z14 we introduced vector float variant and vector max/min as part of vector enhancement facility 1.
with my previous patches #116779, #116669
we have already added support to z14 and above generations.

this patch supports z13 and previous generations

[risc-vv]

@dotnet/samsung Could you please take a look? These changes may be related to riscv64.

[kasperk81]

tab indentation

[saitama951]

@uweigand can you please review this?

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[uweigand]

In addition to the inline comments, you should also fix this:

#define MONO_ARCH_SIMD_INTRINSICS mono_hwcap_s390x_has_vec

and define it to just 1 like everywhere else, since this is not actually evaluated at run-time.

[uweigand]

This version looks good to me now from a s390x target perspective.

[saitama951]

@akoeplinger can this be merged?

[akoeplinger]

/ba-g failures are unrelated to s390x changes

[saitama951]

@akoeplinger can we backport this to release/10.0 as well?

[akoeplinger]

@lewing do we have a policy for changes which only touch community-supported arch code?

[saitama951]

@lewing gentle ping.

@lewing do we have a policy for changes which only touch community-supported arch code?

[giritrivedi]

@akoeplinger , @lewing - Can we have this backported ? or is there a policy which restricts us from backporting ?

[lewing]

/backport to release/10.0

[github-actions]

Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17413301220