Use new universal generator scripts for pi0 and pions

Use new universal generator script run_emcal_barrel_particles.sh for https://eicweb.phy.anl.gov/EIC/benchmarks/detector_benchmarks/-/blob/master/benchmarks/barrel_ecal/config.yml#L1-11 instead of emcal_barrel_pi0.cxx and emcal_barrel_pi0_reader.cxx in https://eicweb.phy.anl.gov/EIC/benchmarks/detector_benchmarks/-/blob/master/benchmarks/barrel_ecal/run_emcal_barrel_pi0.sh#L33-39 (same for run_emcal_barrel_pions.sh)