dim: Migrate to Gitlab

- Use the https url so we don't require everyone to have their gitlab
  accounts ready already. Otherwise we'd need to gate migrating
  maintainer-tools on migrating all the drm kernel repos, and I'd
  really like to partition the migration. Also, we want to reduce
  maintainer-tools committers anyway, to shrink the attack surface a
  lot.

  Committers need to either set up the http access tokens, or set up
  ssh certificates and change their remote for the maintainer-tools
  repo.

- For testing, you can undo this auto-update using

$ git remote remove maintainer-tools ; git branch -u drm-tip/maintainer-tools

- My plan is that we push an immediate revert of this code to the
  gitlab repo (and only there) so it doesn't stick around.

- fd.o admins recommended that we don't do a read-only copy of
  maintaienr-tools at the old-place, since it's not a 1:1 match. For
  everything else we're going to migrate there will be a read-only
  copy with all urls working nicely, maintainer-tools is the only
  exception here.

v2: Don't forget about dim_setup.

v3: Update all the urls in docs!

v4: Also update the new maintainer-tools repo in dim_uptodate (Jani).

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Daniel Stone <daniels@collabora.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com> (v2)
Reviewed-by: Daniel Stone <daniels@collabora.com> (v2)
Reviewed-by: Sean Paul <seanpaul@chromium.org> (v3)
Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>