PADRE-6: Add AntennaFlagger step

The newly added AntennaFlagger step implements the preflagger.baselines functionality of the PreFlagger step, with a better performing alternative implementation based on regular expressions. tAntennaFlagger provides a basic test for this new step. We also integrated the flagging functionality of the AAARTFAAC-12 pipeline, which consists of separate calls (aoquality, aoflagger, a Python script and DP3) into the AntennaFlagger step. This approach is not only much simpler, but also much faster. This automated flagging option can be enabled by setting the flagging parameter.

See also these two merge requests: !667 (merged) and !668 (merged)