[PWGCF] Add photons and pi0s to femto framework

[ariedel-cern]

This PR contains adds the following features to the femto framework:

• Add support for PCM photons to femto-producer
• Add QA task for photons
• Add producer task for resonances decaying into 2 photons
• Adding QA task for resonances decaying into 2 photons

[github-actions]

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

[alibuild]

Auto-approving on behalf of @ariedel-cern.

[alibuild]

Error while checking build/O2Physics/code-check for fec2f81 at 2026-10-04 22:46:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 4 errors and 1 warnings.'
Found 4 errors and 1 warnings.
++ [[ 4 -gt 0 ]]
++ cat /sw/BUILD/4166b5b49f331d570eab7fcd0c0fc6322102161d/O2Physics-code-check/errors.txt
PWGCF/Femto/Core/photonBuilder.h:43:1: error: included header cstdint is not used directly [misc-include-cleaner,-warnings-as-errors]
PWGCF/Femto/Core/photonHistManager.h:90:16: error: no header providing "std::array" is directly included [misc-include-cleaner,-warnings-as-errors]
PWGCF/Femto/Tasks/femtoPhotonQa.cxx:30:1: error: included header HistogramSpec.h is not used directly [misc-include-cleaner,-warnings-as-errors]
PWGCF/Femto/Tasks/femtoPhotonQa.cxx:35:1: error: included header map is not used directly [misc-include-cleaner,-warnings-as-errors]
++ [[ 1 -gt 0 ]]
++ cat /sw/BUILD/4166b5b49f331d570eab7fcd0c0fc6322102161d/O2Physics-code-check/warnings.txt
PWGCF/Femto/Core/photonBuilder.h:331:38: warning: 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]
++ [[ 4 -gt 0 ]]
++ exit 1
--

Full log here.

[ariedel-cern]

Fixing code check errors here: #18171