Migrate DRAW_ZMUMU_SkimmingTool to data handles.
requested to merge goetz/athena:PrimaryDPDMaker_master_migrate_zmumu_skimming_tool_to_dh into master
Use data handles instead of direct storegate access. Also made mutable counters atomic to allow the tool being used in reentrant algorithms.
This addresses part of ATLASRECTS-6090.