Add EventInfoBeamSpotDecoratorAlg to BeamSpotConditionsConfig

One of the differences found by the test_trf_q442_r2a_ca_mt_compare.sh are the missing {{EventInfo}} decorations in teh output AOD of the CA-based job. The algorithm decorating the {{xAOD::EventInfo}} object was missing in the CA-config.

This MR adds it to the BeamSpotConditionsConfig whose main purpose is reading the beam-spot information from the database. I am a bit unsure if this is the best place to add it. In the old-style configuration it was scheduled in RecExCommon_topOptions.py between system-rec and combined-rec.