Merge branch 'BMGforCalibStream' into '21.1'

...rol/AthAllocators/AthAllocators/ATLAS_CHECK_THREAD_SAFETY

Control/AthContainersRoot/share/AuxStoreRoot_test.ref

Control/AthenaKernel/AthenaKernel/ATLAS_CHECK_THREAD_SAFETY

Control/AthenaKernel/share/ClassName_test.ref

...rol/DataModelRoot/DataModelRoot/ATLAS_CHECK_THREAD_SAFETY

Control/SGMon/SGAudCore/SGAudCore/ATLAS_CHECK_THREAD_SAFETY

...MuonSegmentMakerTools/MdtSegmentT0Fitter/doc/packagedoc.h

...gAlgorithms/TrigL2MuonSA/TrigL2MuonSA/MdtDataPreparator.h

...ger/TrigAlgorithms/TrigL2MuonSA/src/MdtDataPreparator.cxx

Trigger/TrigSteer/ViewAlgs/src/SplitViewPerRoI.cxx