cmd/go: add GOFIPS140 to 'go help environment'

cmd/go: add GOFIPS140 to 'go help environment'

Also re-sort the various lists. (All lists should be sorted.)
The linked page https://go.dev/security/fips140 has yet
to be written, but soon.

For #70123.

Change-Id: Ica5bbf5bd29e9136c2a49d3099d6e0e018c36145
Reviewed-on: https://go-review.googlesource.com/c/go/+/629816
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>