Making it easier to run bindings that are not in the main repo

We've already seen interest in the community in creating third-party bindings, which will live outside the main FoundationDB repo. It's tricky to test these bindings with the current binding tester implementation, because it relies on a list of known testers that are defined in python code inside of the core binding tester. I think we should consider making this more flexible, like having an option to define a new binding tester on the command line or moving the known tester into a configuration file that can itself be passed on the command line.

Start by reading the core binding tester's Python code and its list of known testers. Compare the command-line option and configuration-file approaches described in the issue, then define completion as allowing a third-party binding tester outside the main repository to run through the existing tester workflow.

Written by the indexing model from the issue text.