Standardize on localhost for praefect and gitaly addresses

the main gitaly and praefect ports, as well as the gitaly prometheus and praefect prometheus ports are handled by the cloudflare tableflip library, which will refuse to upgrade if a different address is used with the same port. By standardizing to localhost for these addresses (and update the docs accordingly), we minimize the situation where sometimes 0.0.0.0:1234 is used, and a user changes this to localhost:1234 per the docs, and the upgrade fails.

fixes: https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/5223