Partially addresses #47424.

This reverts commit 4d9a3f42, reversing
changes made to ecf9c145.

Signed-off-by: Rémy Coutable <remy@rymai.me>

ObjectStore uploader requires presence of associated `uploads` record
when deleting the upload file (through the carrierwave's after_commit
hook) because we keep info whether file is LOCAL or REMOTE in `upload`
object.

For this reason we can not destroy uploads as "dependent: :destroy" hook
because these would be deleted too soon. Instead we rely on
carrierwave's hook to destroy `uploads` in after_commit hook.

But in before_destroy hook we still have to delete not-mounted uploads
(which don't use carrierwave's destroy hook). This has to be done in
before_Destroy instead of after_commit because `FileUpload` requires
existence of model's object on destroy action.

This is not ideal state of things, in a next step we should investigate
how to unify model dependencies so we can use same workflow for all
uploads.

Related to #45425

1. we don't want to migrate all existing groups
2. we generate the token when showing the runners page, as this is the
   first time that the token will be used.

This reverts the addition of the "goldiloader" Gem and all use of it.
While this Gem is very promising it's causing a variety of problems on
GitLab.com due to it eager-loading too much data in places where we
don't expect/can handle this. At least for the time being this means we
have to go back to manually fixing N+1 query problems, but at least
those should not cause a negative impact on availability.

Goldiloader is great, but has several issues with has_many :through relations:

* https://github.com/salsify/goldiloader/issues/12
* https://github.com/salsify/goldiloader/issues/14
* https://github.com/salsify/goldiloader/issues/18

Rather than try to figure out which applies in each case, we should just do the
drudge work of manually disabling autoloading for all relations of this type. We
can always use regular preloading for specific cases, but this way we avoid
generating invalid queries through Goldiloader's magic.

This reverts commit 54a575f1, reversing
changes made to c63af942.

Move uploads to object storage

Closes #4163

See merge request gitlab-org/gitlab-ee!3867

Comments from code review applied. Also switched forked_from_project and ForkedProjectLinks to ForkNetworkMember