Fix GitLab code intelligence on blob pages
Created by: lguychard
Similarly to #8134, the new URL scheme (/owner/projectName/-/blob
instead of /owner/projectName/blob
) has now been adopted by GitLab on blob pages as well, which breaks code intelligence: https://gitlab.com/gitlab-org/gitlab/issues/202337#note_283709888
This PR adds handling for both URL schemes on all page types (MR, commit, files), with unit tests to validate it.