Would be nice: Combined prtest/private job/official job types

[mmitche]

Right now we have to have individual jobs for prtest and official, to keep the badges (and general job views) clean. We would also have to do the same for private jobs (if available) since they couldn't be shared with PR tests. This is clunky and involves a lot of duplicated job logic. Would be awesome to have a Jenkins plugin that that allows some kind of job type.