[dev.simd] simd: update CPU feature APIs

[dev.simd] simd: update CPU feature APIs

This CL also updates the internal uses of these APIs.

This CL also fixed a instable output issue left by previous CLs.

Change-Id: Ibc38361d35e2af0c4943a48578f3c610b74ed14d
Reviewed-on: https://go-review.googlesource.com/c/go/+/720020
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>