windows: add IsProcessorFeaturePresent and processor feature consts

For golang/go#76791

Change-Id: I1594c4868262c78d40e1ebd883a01a71236e4981
Reviewed-on: https://go-review.googlesource.com/c/sys/+/740500
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>