This commit also excludes gitlab-shell from dependencies:

Gitaly specifies Gitlab Shell as a dependency as well in order
to use gitlabnet client to perform API endpoints to Gitlab Rails.
As a result, Gitlab Shell requires Gitaly -> Gitaly requires an
older version of Gitlab Shell -> that version requires an older
version of Gitlab Shell, etc. Let's use exclude to break the
chain earlier

While gitlab-shell currently has a major version of v14, the module path
it exposes is not using that major version like it is required by the Go
standard. This makes it impossible for dependents to import gitlab-shell
as a dependency without using a commit as version.

Fix this by changing the module path of gitlab-shell to instead be
`gitlab.com/gitlab-org/gitlab-shell/v14` and adjust all imports
accordingly.

Changelog: fixed

- Use console package to format the errors in gitlab-sshd
- Suppress internal Gitaly errors in client output

Before this change, the GitLab internal API could use a boolean
response field to indicate whether gitlab-shell should make
sidechannel connections go Gitaly. We now ignore that response field
and always use sidechannel connections.

When gitlab-sshd has been introduced we've started running our
own SSH server. In this case we're able to cache and reuse
Gitaly connections and Registry.

It helps to reduce memory usage.

If the GitLab API returns an allowed response with use_sidechannel set
to true, gitlab-shell will establish a sidechannel connection and use
SSHUploadPackWithSidechannel instead of SSHUploadPack. This is an
efficiency improvement.

It adds correlation ids wherever possible