cmd/go/internal/modload: do not resolve an arbitrary version for 'go list --versions'
If we don't actually require the listed module, we previously
implicitly resolved "latest", but also (erroneously) forgot to apply
exclusions and retractions for it. But there is really no need to
resolve "latest" in this case at all — now we omit the version from
the reported module info entirely.
Fixes #44296
Change-Id: Id595f52f597c7213bd65b73bf066a678d9e1d694
Reviewed-on: https://go-review.googlesource.com/c/go/+/297150
Trust: Bryan C. Mills <bcmills@google.com> Reviewed-by: Michael Matloob <matloob@golang.org>