WIP: Add a new "htcondor" runner that utlizes the python htcondor version 2 bindings

[bgruening]

This PR is WIP, but maybe people want to play with it.

The idea would be to include htcondor as a new runner and then gradually deprecate/remove the old condor runner.

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Add a new HTCondor job runner that uses the htcondor2 (Python v2) API.

Supports optional remote collector/schedd/config overrides.

• Should the unit tests be dropped?
• Are the integration tests fine? I would need help here, I think.
• There is something fancy integrated for ITs ... not sure if this is too fancy.

Admin documentation is included. There is also a manually testing steps description using the htcondor/mini container.
Should this be turned into an integration test?

So many questions, feedback welcome.

Upstream Python bindings docs: https://htcondor.readthedocs.io/en/latest/apis/python-bindings/api/version2/index.html

[jmchilton]

Should the unit tests be dropped?

Yes I think. That or we should keep a version of them but generalize all the plumbing somehow so we could test multiple job runners using some of those fixtures and just mock out the htcondor interaction stuff.