[PWGCF] Fix bugs for RecSim mode and add multiparticle correlation calculation

[meiALICE]

Fix bugs on filling histograms in RecSim mode.

Add two and recursion for multiparticle correlation.

Renaming things and other improvements.

[github-actions]

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

[alibuild]

Error while checking build/O2Physics/code-check for e6a79d6 at 2026-09-19 13:34:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 1 errors and 8 warnings.'
Found 1 errors and 8 warnings.
++ [[ 1 -gt 0 ]]
++ cat /sw/BUILD/89dc88378212601c38510532bd22ffbd84b04cb8/O2Physics-code-check/errors.txt
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:16:1: error: included header EventSelectionParams.h is not used directly [misc-include-cleaner,-warnings-as-errors]
++ [[ 8 -gt 0 ]]
++ cat /sw/BUILD/89dc88378212601c38510532bd22ffbd84b04cb8/O2Physics-code-check/warnings.txt
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:191:5: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:198:5: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:204:5: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:215:5: warning: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays]
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:290:22: warning: statement should be inside braces [readability-braces-around-statements]
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:295:25: warning: statement should be inside braces [readability-braces-around-statements]
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:328:14: warning: redundant boolean literal in conditional return statement [readability-simplify-boolean-expr]
PWGCF/MultiparticleCorrelations/Tasks/multiparticleCorrelationsMei.cxx:329:7: warning: do not use 'else' after 'return' [readability-else-after-return]
++ [[ 1 -gt 0 ]]
++ exit 1
--

Full log here.

[abilandz]

Please address the remaining suggestions from code-check along the next PR. This one is approved now!