add photon selection to EXOT8 and add photon trigger variables to EXOT6

This MR affects two derivations: EXOT6 and EXOT8

Changes to EXOT6: the four vector of online photons and jets is stored and offline photons are decorated with the trigger matching information

Changes to EXOT8: an additional selection to the jet selection was implemented that triggers on photons to select high-pT photon + large-R jet events. This selection will be used by the ISR+dijet teams (b-tagged and untagged).

The changes were discussed with @guescini @kkrizka @rateixei and @mswiatlo. Also tagging @jveatch for his information.