COB-184: Add tMultipleBeamFormers

This is an integration test for the LMM functionality. It first runs 4 separate beamFormer pipelines (each with its own parset) as a reference, followed by a pipeline where the beamFormers run simultaneously (with a single parset). The test passes when the output is identical.

This test uses commissioning data that is not available on all COBALT nodes. Whenever this data is not found, the test is skipped.

Two specific cases are tested as well: station subset in FE mode and subband selection. These cases failed before, but have now been fixed.