Split out repository unit settings

This splits out the repository unit settings (formerly "Advanced
settings" under the repository settings page) into their own, separate
page.

The primary reason for this is that the settings page became long and
complicated, with a structure that not always made sense. A secondary
reason is that toggling units on and off should not necessarily be an
"advanced" setting. We want to make doing that easier, and having the
units on their own page helps with that.

This is basically a refactor, there is no new functionality introduced,
just an extra pair of routes for the new page, and the supporting code.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>

options/locale/locale_en-US.ini

@@ -2066,6 +2066,9 @@ settings.mirror_settings.push_mirror.remote_url = Git Remote Repository URL
 settings.mirror_settings.push_mirror.add = Add Push Mirror
 settings.mirror_settings.push_mirror.edit_sync_time = Edit mirror sync interval
 
+settings.units.units = Repository Units
+settings.units.overview = Overview
+
 settings.sync_mirror = Synchronize Now
 settings.pull_mirror_sync_in_progress = Pulling changes from the remote %s at the moment.
 settings.push_mirror_sync_in_progress = Pushing changes to the remote %s at the moment.