[dev.simd] simd, internal/cpu: support more AVX CPU Feature checks

[dev.simd] simd, internal/cpu: support more AVX CPU Feature checks

This CL adds more checks, it also changes HasAVX512GFNI to be exactly
checking GFNI instead of being a virtual feature.

This CL copies its logic from x/sys/arch.

Change-Id: I4612b0409b8a3518928300562ae08bcf123d53a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/688276
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>