Refs #9711. Refactored PoldiMerge to use MergeRuns

Consequently, WorkspaceGroups can be handled now as well.
Refs #9711. Instruments are compared as well now.
Refs #9711. Merging new data files

As explained in #10090, the measured chopper speed is sometimes a bit off on new data files. That's why the speed has to be cleaned up for now.
Merge remote-tracking branch 'origin/feature/9711_refactor_poldi_merge'