[PWGEM/Dilepton] add a simple task to check PV in MC

[dsekihat]

[PWGEM/Dilepton] add a simple task to check PV in MC

[github-actions]

O2 linter results: ❌ 3 errors, ⚠️ 2 warnings, 🔕 0 disabled

[alibuild]

Auto-approving on behalf of @dsekihat.

[alibuild]

Error while checking build/O2Physics/code-check for d59c09c at 2026-08-08 16:06:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 2 errors and 0 warnings.'
Found 2 errors and 0 warnings.
++ [[ 2 -gt 0 ]]
++ cat /sw/BUILD/2e32fa53f5d43993e881034c27af74c386c365c7/O2Physics-code-check/errors.txt
PWGEM/Dilepton/Tasks/testPV.cxx:20:1: error: included header AnalysisHelpers.h is not used directly [misc-include-cleaner,-warnings-as-errors]
PWGEM/Dilepton/Tasks/testPV.cxx:89:44: error: no header providing "TH1" is directly included [misc-include-cleaner,-warnings-as-errors]
++ [[ 0 -gt 0 ]]
++ [[ 2 -gt 0 ]]
++ exit 1
--

Full log here.