[C++] Neon not enabled on Windows ARM64

[pitrou]

Describe the enhancement requested

It seems that, currently, Neon is not enabled at all on Windows ARM64 builds:
https://github.com/apache/arrow/actions/runs/25043252865/job/73351674163?pr=49756#step:11:377

The reason was lack of xsimd support. However, xsimd now supports Windows ARM64 on its main branch.

So we can probably re-enable Neon on Windows once a new xsimd version is released.

Component(s)

C++

[pitrou]

cc @jgiannuzzi