Allow automatically triggering the pipeline for radv jobs in forks
While we are getting ready to put runners for radv testing in the main project, we would like to let the radv developers test with our currently limited amount of available runners in their forks.
This MR introduces a mechanism by which, if a fork sets a UI_FORKED_AUTOMATIC_JOBS variable in GitLab's UI, certain jobs will be triggered automatically in the branches of the fork.
By now, only "radv" is supported and the only jobs that would be run automatically are the ones "needed" by the radv test jobs, and the radv test jobs.
The idea is that this would be a temporal modification to be removed once we have a more powerful setting that will allow the pre-merge testing in the limited amount of time agreed for the main project. However, this can be extended to use other keywords beyond "radv".