[PWGJE] PhotonMeson/Tasks/compconvbuilder: Fix linter and includes

- Add missing includes using the IWYU principle
- Remove unused includes
- Fix O2Linter errors, except one magic number error, which was silenced: `if (daughters.size() != 2)`. This one is not a magic number imo.
- Fix include parenthese for ("outside") O2 headers

Author: mhemmer-cern