Update/Cleanup of the TrigTauRec package

This MR addresses the cleanup/documentation of the TrigTauRec package, in preparation for the HLT GNTau implementation. This is part of a series of MRs that will be undrafted sequentially.

No HLT Tau Triggers will be used in the low-mu pp or HI data-taking runs, so we can open these MRs now, which are needed before we start validating the new HLT GNTau.

Amongst the most important changes, we can list:

• Cleanup of the TrigTauRecMerged algorithm:
  • Better separated the calo-only reconstruction (for the CaloMVA step), and the xAOD::TauJet-seeded reconstruction (for the Precision step).
  • Removed some unused skeleton code from previous versions. This is a much better clean slate for the soon-to-come changes (3-step tracking, preselections, etc...).
  • Added support for monitoring multiple TauId scores.
• Updated online TauID score monitoring histograms:
  • The histograms' names have been overridden to be the same as in the current Athena release to allow for an HLT Reprocessing validation round with complete reference comparisons.
  • After the changes are validated, we'll update the histogram names.
• Added ONNX-based TauID inferences.
• Moved HLT TauID config flags to sub-directories:
  • Each algorithm will have a dedicated sub-directory for it's configuration
  • The required LVNN-based or ONNX-based infrastructure is automatically loaded and configured based on the config-flags for each algorithm. This allows for quick testing and deployment of new algorithms!
• Moved the TrigTauCaloRoiUpdater and TrigTauTrackRoiUpdater algorithms from the TrigTauHypo to the TrigTauRec package, since they are not hypothesis algorithms or tools (this caused some confusion in the past to newcomers).
• Added a README.md, and descriptive comments to the configuration code of the TrigTauRec package.
• Added support in the EDM for additional TauID scores and WPs.
• General code linting.

The changes were validated by comparing event counts and online/offline monitoring histograms for 10k mc23e ttbar/g*tautau/Ztautau events.

With this last MR, we're ready to deploy the HLT GNTau ID with minimal changes as soon as it's ready 😄 @asudhaka