crypto/fips140: new package

crypto/fips140: new package

This package holds only the Enabled() function.

Updates #70123

Change-Id: If0e731724d9997001fa52002fa6ae72df4eb16ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/631017
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Daniel McCarney <daniel@binaryparadox.net>