Add ability to change the default clone protocol, useful when SSH certificates are in use

Now that my !19911 (merged) is merged and we're running with SSH certificates I noticed that the clone protocol on project pages is always https.

This is because of the change discussed in https://gitlab.com/gitlab-org/gitlab-ce/issues/3504#note_2872589 implemented in https://gitlab.com/gitlab-org/gitlab-ce/commit/88217029fc37e972fd84aec7eb9a77247a9532bf

If I upload an SSH key it'll show "ssh" as the default. Similar to my #49953 (closed) this is probably something that should get a global config setting, maybe we should just add one saying "ssh certificates are in use" to cover this, the issue in #49953 (closed), and anything else that may come up.