The work of running full vet on std and cmd during local development
has moved to go test, which of course runs during all.bash.

For errors in other GOOS/GOARCH combinations, the misc-compile
builders (running buildall.bash) also now run go vet std cmd.

The vetall builder need not do anything anymore.
Make it a no-op until it can be retired, and remove
cmd/vet/all and its special case in the go command.

Fixes #31916.

Change-Id: I8f30d184c382ea7c2c8f520e5618f680db633968
Reviewed-on: https://go-review.googlesource.com/c/go/+/176440
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>