cmd/go: add Shell.RemoveAll
There are quite a few places that perform their own command logging
and then use os.RemoveAll. Unify (nearly) all of these into
(*Shell).RemoveAll, like many of the other internal implementations of
basic shell operations.
Change-Id: I94a2cbd9dc150a4c94a4051c42ce8e86dcc736fd
Reviewed-on: https://go-review.googlesource.com/c/go/+/536099
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Austin Clements <austin@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>