[PWGLF] Update on Event and Signal Loss

[zhengqi-w]

• [General] Update with the Event Split calculation and the Event,Signal Loss histograms
• Change the Histogram definition and filling steps of Generated Events with at least one recon. event. (since only generated events which has been reconstructed can get the physical CentralityFT0C information)
• Change the filling scheme for reconstructed MC collisions (since one generated collision may be reconstructed more than once) calculating the Event Splitting part of Event Loss coefficient.

[github-actions]

O2 linter results: ❌ 25 errors, ⚠️ 8 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/o2 for aa07657 at 2026-05-13 07:26:

## sw/BUILD/O2Physics-latest/log
c++: fatal error: Killed signal terminated program cc1plus
ninja: build stopped: subcommand failed.

Full log here.

[maciacco]

@zhengqi-w approving now, please check the o2 linter errors in the next iteration