Skip HLT result building for rejected events
Optimise HLT result building by skipping almost everything if the event is rejected. Additionally, update the units and range of the timing histogram and remove all other HLTResultMTMaker histograms which are redundant (downstream code monitors these variables better).
This improves HLT execution time by ~10 ms for rejected events, which is significant because:
- most events processed by HLT online are rejected (that's the main point of HLT)
- a large fraction of the rejected events takes only a few tens of ms to process (see e.g. here)