OutputStreamAthenaPool+RecJobTransforms+PyJobTransforms+TrfTestsART: Add CA-based AODMerge
As part of ATEAM-822, this MR adds a CA-based AODMerge logic.
The event-data agree between the files merged w/ the old-style and the new-style configurations apart from those variables that are "randomly" dropped in the old-style configuration (merge jobs adding/dropping/changing variables always made me unhappy).
The meta-data agree 99%. A handful of variables, namely amiTag, beamEnergy, and beamType from FileMetaData as well as AtlasRelease in TagInfo do not fully agree. These differences will be clearly highlighted by the ART test. We should resolve these and improve the meta-data handling in the new-style configuration in the (not-so-distant) future.