AST-1540 Deduplicate test directory creation

CMakeLists.txt

ddecal/test/integration/tBdaDdeCal.py

ddecal/test/integration/tDDECal.py

ddecal/test/integration/tIDGPredict.py

parmdb/test/integration/tShowSourceDb.py

pythondp3/test/integration/tMakeMainSteps.py

scripts/test/utils.py

steps/test/integration/tApplyBeam.py

steps/test/integration/tApplyCal2.py

steps/test/integration/tBdaExpander.py

steps/test/integration/tBdaPredict.py

steps/test/integration/tClipper.py

steps/test/integration/tColumnReader.py

steps/test/integration/tDemix.py

steps/test/integration/tGainCal.py

steps/test/integration/tGainCalH5Parm.py

steps/test/integration/tIDGImager.py

steps/test/integration/tMsIn.py

steps/test/integration/tMsOut.py

steps/test/integration/tMultiApplyCal.py