cmd/go: move two vcs test repos to vcs-test.golang.org

Follow-up to CL 174061. This also fixes a break after GOSUMDB
was introduced.

Updates #31946
Updates #31673
Updates #31287
Updates #27171

Change-Id: I8e91e857f301b6b73cc90f2f2c68523412e22b46
Reviewed-on: https://go-review.googlesource.com/c/go/+/176417


Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>