Tau Trigger online monitoring update and Reco/Hypo code cleanup

This MR cleans up the TrigTauRecMerged tool used in the HLT Tau Trigger reconstruction, and the TrigEFTauMVHypoTool, used in the final trigger step hypothesis test. The code was refactored, updating the internal naming conventions. Some preliminary preparation towards the implementation of the HLT GNTau was also done.

The online monitoring histograms were also updated (updating titles, labels, etc). Duplicated histograms were removed (not used in P1). No changes were made to the histogram names, to avoid breaking the references used in P1 (they will be updated after the HI data-taking starts, where no HLT Tau Triggers are used).