Add new func Unzip, which is Download (= download+unzip)
without the download. This will be used for unpacking the
FIPS module zips, which are part of the Go distribution,
not downloaded.
Change-Id: Ia04f8c376db8cb1cf27acb5567dd256afb10f410
Reviewed-on: https://go-review.googlesource.com/c/go/+/629200
Auto-Submit: Russ Cox <rsc@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>