libgo: cmd/go: use 'gcloud storage cp' instead of 'gsutil cp'

In some misguided attempt at "cleanup", Google Cloud has
decided to retire 'gsutil' in favor of 'gcloud storage' instead
of leaving an entirely backwards-compatible wrapper so
that client scripts and muscle memory keep working.

In addition to breaking customers this way, they are also
sending AI bots around "cleaning up" old usages with scary
warnings that maybe the changes will break your entire world.
This is even more misguided, of course, and resulted in us
receiving CL 748661 (originally GitHub PR golang/gofrontend#13)
and then me receiving a private email asking for it to be merged.

It was easier to recreate the 4-line CL myself than to
enumerate everything that was wrong with that CL's
commit message.

I hope that only Google teams are being subjected to this.

This is based on https://go.dev/cl/748900 from the main Go repo by Russ.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/749000

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-6e421340885c87c4987f27be4a16b7bedb86faaa
+d7cb797c46170ea43381064745514fd597cb8d7d
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/cmd/go/internal/modload/query_test.go

@@ -88,7 +88,7 @@ var queryTests = []struct {
 		git commit -m 'after v2.5.5' status
 		git checkout master
 		zip -r ../querytest.zip
-		gsutil cp ../querytest.zip gs://vcs-test/git/querytest.zip
+		gcloud storage cp ../querytest.zip gs://vcs-test/git/querytest.zip
 		curl 'https://vcs-test.golang.org/git/querytest?go-get=1'
 	*/
 	{path: queryRepo, query: "<v0.0.0", vers: "v0.0.0-pre1"},

libgo/go/cmd/go/testdata/script/mod_get_pseudo_other_branch.txt

@@ -64,4 +64,4 @@ git checkout master
 git merge b -m merge
 
 zip -r ../tagtests.zip .
-gsutil cp ../tagtests.zip gs://vcs-test/git/tagtests.zip
+gcloud storage cp ../tagtests.zip gs://vcs-test/git/tagtests.zip

libgo/go/cmd/go/testdata/script/mod_get_pseudo_prefix.txt

@@ -61,4 +61,4 @@ git add status
 git commit -m 'after last tag'
 
 zip -r ../prefixtagtests.zip .
-gsutil cp ../prefixtagtests.zip gs://vcs-test/git/prefixtagtests.zip
+gcloud storage cp ../prefixtagtests.zip gs://vcs-test/git/prefixtagtests.zip

libgo/go/cmd/go/testdata/script/mod_retract_pseudo_base.txt

@@ -59,4 +59,4 @@ git mv p.go q.go
 git commit -m 'trivial change'
 
 zip -r ../retract-pseudo.zip .
-gsutil cp ../retract-pseudo.zip gs://vcs-test/git/retract-pseudo.zip
+gcloud storage cp ../retract-pseudo.zip gs://vcs-test/git/retract-pseudo.zip