In BuildRawEvent algo, add 3 histos for overlap stats in AllowOverlap mode

Of interest to @c.sturm @i.deppner

Plots are added as soon as AllowOverlap mode is enabled and histograms are enabled.
Plots found in same folder as the other histos.

• fhOverEventShare shows the ratio of events in overlap in the processing runs by the mean value of a 2 bins histogram
• fhOverEventShareTs is a Profile showing the smae value as function of TS in processing run (not absolute TS index in recorded run!)
• fhOverEventSizeTs is a 2D histogram showing for each TS the distribution of the size of the overlapping region between 2 events in overlap (maximal value should more or less fit with the largest selection window size)

All these are probably highly dependent on the chosen trigger definition and selection windows!

Not sure to whom this should be assigned.