Allow for scaling true energy in IRFs to assess energy-scale systematics

[deborahDOR]

Modifications of the code for the consideration of systematics in the energy. The goal is to generate modified IRFs due to the effect of a lower or higher light efficiency in the system (telescope + atmosphere) with respect to simulations, by scaling the true energy values in MC simulations.

The changes are:

• A new argument in the DataBinning Component in lstchain/io/event_selection.py : "scale true energy" (value that will be applied in the true energy values of the events of the MC files)
• Add "scale true energy" in the irf_dl3_config_tool.json in the DataBinning section (only if the value is different from 1, it will be considered in the computation).
• Changes in lstchain_create_irfs_files.py to modify the values when pyrif commands are used. Added comments to describe how it can be used and its effects.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 73.36%. Comparing base (7f92595) to head (221aaf7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1261 +/- ## ========================================== + Coverage 73.28% 73.36% +0.07% ========================================== Files 134 134 Lines 14084 14126 +42 ========================================== + Hits 10321 10363 +42 Misses 3763 3763 ```

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