[PWGCF] fix labeled array configurable in twoParticleCorrelationsMPI.cxx

[EmilGorm]

Fix labeled array configurable in twoParticleCorrelationsMPI.cxx
Add nch/cent axis support in flowGfwNonflow.cxx
Use MCLabels of reconstructed particles for rejection of generated daughter eta range in flowGenericFramework.cx

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 0 warnings, 🔕 1 disabled

[vkucera]

where is missing in the title.

[alibuild]

Error while checking build/O2Physics/code-check for 580474d at 2026-07-22 19:01:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 4 errors and 0 warnings.'
Found 4 errors and 0 warnings.
++ [[ 4 -gt 0 ]]
++ cat /sw/BUILD/69553fccc327823ce13069ee67b8cacd924d10e1/O2Physics-code-check/errors.txt
PWGCF/GenericFramework/Tasks/flowGfwNonflow.cxx:246:43: error: initializer for member 'corrconfigs' is redundant [readability-redundant-member-init,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwNonflow.cxx:250:41: error: initializer for member 'multipletKeys' is redundant [readability-redundant-member-init,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwNonflow.cxx:527:122: error: the parameter 'xAxis' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwNonflow.cxx:587:47: error: use designated initializer list to initialize 'MultipletConfig' [modernize-use-designated-initializers,-warnings-as-errors]
++ [[ 0 -gt 0 ]]
++ [[ 4 -gt 0 ]]
++ exit 1
--

Full log here.