[PWGEM,PWGHF] Clean up code-check errors and warnings

[mhemmer-cern]

Clean up some code-check errors and warnings in the PWGEM/PhotonMeson/Utils part. Resulting changes affected also one code in HF so I touched that one file and fixed the things there too. I hope that's okay.

[github-actions]

O2 linter results: ❌ 181 errors, ⚠️ 300 warnings, 🔕 16 disabled

[mhemmer-cern]

@vkucera something is wrong with the code-check result here.
PWGEM/PhotonMeson/Utils/ClusterHistograms.h:19:10: error: 'PWGEM/PhotonMeson/Core/EMCPhotonCut.h' file not found [clang-diagnostic-error]
The file is there and otherwise wouldn't compilation break?
PWGEM/PhotonMeson/Utils/ClusterHistograms.h:27:1: error: included header TH2.h is not used directly [misc-include-cleaner,-warnings-as-errors]
TH2 is used in line 74
array is used in line 117...
and so on.

Locally when checking my branch with these commit vs upstream/master I am not getting any of these false errors.

[vkucera]

@mhemmer-cern Indeed, I cannot reproduce it either locally. It seems like Clang-Tidy cannot find the correct compilation command for the header in the database.

[mhemmer-cern]

@mhemmer-cern Indeed, I cannot reproduce it either locally. It seems like Clang-Tidy cannot find the correct compilation command for the header in the database.

Then I will mark this a ready for review.