Fix trigger filter for data overlay
Rewrite the BSFilter algorithm to use the TrigDecisionTool for
trigger-based event filtering on RAW. This ensure compatibility with
past and future data. Change the --triggerBit transform argument from
the CTP ID (240) to the CTP item name ("L1_ZB"), which is guaranteed to
work also if the item ID changes.
Also apply some general code cleanups.
Closes ATLASSIM-5419.