Sort HLT and L1 histogram x-axes alphabetically
This addresses issues discussed in [ATR-21172] and [ATR-19976] by alphabetically sorting the x-axes of the histograms monitoring L1 items and HLT chains.
Currently, the histograms monitoring L1 items and HLT chains which are fired in the run, are filled in the order the events happen to be processed. This means that the shape of the histograms can differ quite dramatically for reasons purely to do with process ordering, which is clearly not the desired behaviour.
After the change, we will have these improvements:
- Reprocessing the same run without changing the menu will result in an identical histogram.
- If the menu is changed (by removing or adding a few chains) the x-axis will shift a little bit in a way which is clearly recognisable.
- All histograms from a particular signature will end up together. (With the exception of multi-ele/jet/muon/etc where HLT_2jX_blabla will be closer to HLT_2eX_blabla than to HLT_jX_blabla )
Example of desired behaviour (Run 2 code): https://atlas.web.cern.ch/Atlas/project/trigger/trigcaf/www/ATR-24194-legacy/ResultMon/L1Events.html
What is currently looks like in Run 3 code: https://atlas.web.cern.ch/Atlas/project/trigger/trigcaf/www/ATR-24194-run3/ResultMon/L1Events.html (data and reference disagree artificially even though there was no change).