Move Jenkins jobs to public infrastructure

We should move (or copy) a core set of Jenkins jobs to public infrastructure. At least this should include the nightly core build, the dataloading job and the GVM (pre-commit tests) job.

It's not clear at this point whether the jobs should live on a public Jenkins instance that Cloudera administers (since the jobs are quite heavyweight) or whether they can go on https://builds.apache.org/. We should engage ASF Infra to get their opinion on the best way forward.