[PWGCF] add multiplicity and pT fluctuations task

[orubza]

No description provided.

[github-actions]

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

[alibuild]

Error while checking build/O2Physics/staging for 24171a9 at 2026-08-25 09:06:

## sw/BUILD/O2Physics-latest/log
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGCF/EbyEFluctuations/Tasks/multandptFluctuations.cxx:139:68: error: 'kNoSameBunchPileup' is not a member of 'o2::aod::evsel'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGCF/EbyEFluctuations/Tasks/multandptFluctuations.cxx:141:74: error: 'kIsGoodZvtxFT0vsPV' is not a member of 'o2::aod::evsel'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGCF/EbyEFluctuations/Tasks/multandptFluctuations.cxx:143:72: error: 'kIsGoodITSLayersAll' is not a member of 'o2::aod::evsel'
ninja: build stopped: subcommand failed.

Full log here.

[alibuild]

Error while checking build/O2Physics/o2 for 24171a9 at 2026-08-25 09:10:

## sw/BUILD/O2Physics-latest/log
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGCF/EbyEFluctuations/Tasks/multandptFluctuations.cxx:139:68: error: 'kNoSameBunchPileup' is not a member of 'o2::aod::evsel'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGCF/EbyEFluctuations/Tasks/multandptFluctuations.cxx:141:74: error: 'kIsGoodZvtxFT0vsPV' is not a member of 'o2::aod::evsel'
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGCF/EbyEFluctuations/Tasks/multandptFluctuations.cxx:143:72: error: 'kIsGoodITSLayersAll' is not a member of 'o2::aod::evsel'
ninja: build stopped: subcommand failed.

Full log here.

[SwatiSaha-1997]

Hi @orubza , please do check your PR before committing. Please follow the instructions. I think you are missing a header.

[SwatiSaha-1997]

Please add the missing header file in your .cxx file:
#include "Common/CCDB/EventSelectionParams.h"