Automatically pick the fastest pipeline (lowest ping time) for new jobs

[Asparagirl]

If a new job is created and there are multiple open pipelines, ping them all and give the job to the one with the lowest ping time.

(Props to MrRadar for the suggestion, an improvement on the idea of manually setting country and region for each pipeline.)

[JustAnotherArchivist]

If anything, then each (available) pipeline should ping the target site and the pipeline with the lowest ping to the target site should get the job (rather than the one with the lowest ping to the control node). But in reality, there's almost never more than one slot empty, so this would hardly ever be relevant.