[PWGCF] Added multiplicity study & pt correlations

[MaximVirta]

Added pt spectra and flow multiplicity vs centrality study. Additionally, fixed some magic number errors raised by linter.

[github-actions]

O2 linter results: ❌ 1 errors, ⚠️ 0 warnings, 🔕 3 disabled

[alibuild]

Error while checking build/O2Physics/code-check for 87da907 at 2026-07-30 14:35:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 93 errors and 62 warnings.'
Found 93 errors and 62 warnings.
++ [[ 93 -gt 0 ]]
++ cat /sw/BUILD/c5ad4ece5816693a93cb477a93c93f65bb5215e5/O2Physics-code-check/errors.txt
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:77:78: error: macro argument should be enclosed in parentheses [bugprone-macro-parentheses,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:78:18: error: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:82:21: error: variable 'ptbinning' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:83:7: error: variable 'ptpoilow' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:83:23: error: variable 'ptpoiup' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:84:7: error: variable 'ptreflow' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:84:23: error: variable 'ptrefup' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:85:7: error: variable 'ptlow' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:85:20: error: variable 'ptup' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:86:5: error: variable 'etabins' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:87:7: error: variable 'etalow' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:87:22: error: variable 'etaup' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:88:5: error: variable 'vtxZbins' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:89:7: error: variable 'vtxZlow' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:89:24: error: variable 'vtxZup' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:90:5: error: variable 'phibins' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:91:7: error: variable 'philow' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:92:7: error: variable 'phiup' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:93:5: error: variable 'nchbins' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:94:7: error: variable 'nchlow' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:95:7: error: variable 'nchup' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:96:21: error: variable 'centbinning' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:97:5: error: variable 'nBootstrap' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:98:40: error: variable 'etagapsPtPt' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:99:12: error: variable 'regions' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:100:16: error: variable 'configs' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:101:21: error: variable 'multGlobalCorrCutPars' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:102:21: error: variable 'multPVCorrCutPars' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:103:21: error: variable 'multGlobalPVCorrCutPars' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:106:8: error: constructor does not initialize these fields: ccdb [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:194:57: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:210:10: error: constructor does not initialize these fields: mAcceptance [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:211:5: error: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:262:10: error: constructor does not initialize these fields: tofNsigmaCut, itsNsigmaCut, tpcNsigmaCut [cppcoreguidelines-pro-type-member-init,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:313:39: error: Assigned value is garbage or undefined [clang-analyzer-core.uninitialized.Assign,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:387:136: error: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:388:130: error: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:389:130: error: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:390:136: error: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:396:148: error: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:397:142: error: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer,-warnings-as-errors]
PWGCF/GenericFramework/Tasks/flowGfwV02.cxx:398:142: error: 'data' should be used for accessing the data pointer instead of taking the address of the 0-th element [readability-container-data-pointer,-warnings-as-errors]
[0 more errors; see full log]

Full log here.