[PWGEM] PhotonMeson: Add basic QA for V0Photons

- Add `AreSelectedRunning` function to V0PhotonCuts class, which allows the usage of `EMButFlags` once at the beginning of a process function instead of checking each V0 photon inside the pair loops.
- Add basic QA for V0Photons in the V0PhotonCuts class. To use it one must set the flag by using `setDoQA(true)` AND providing a pointer to the histogram registry of the main task. To initilize the histograms one needs to call `fV0PhotonCut.addQAHistograms(&registry)` in the init function of the task. For proper usage one needs to use `AreSelectedRunning`. It is possible to do it with the single V0 check function IsSelected(), however, not all histograms will be properly filled in that case.
- Fix basic QA inside EMCPhotonCuts

Author: mhemmer-cern