Support release 21: Remove hardcoded variable mapping

We still had a hardcoded list that mapped some b-tagging variables to their isDefaults values. This was a bit of a problem if we wanted to read release 21 files, because some of these were renamed.

This merge request removes that hardcoded default mapping, and replaces it with a json file. I've updated all the configuration files to use it.

I also added a top level python script to run on the upgrade (release 21.9) AOD that @bdong sent me. It schedules a few algorithms that decorate tracks and the BTagging object, adding a few things that b-tagging code exists in r22 but wasn't there in r21.