EgammaxAODHelpers add isFCal helper and tidy code. Use it in LargeClusterMaker and also tidy this one

Merged Christos Anastopoulos requested to merge ATLAS-EGamma/athena:add_is_FCAL_helper into 23.0

EgammaxAODHelpers add isFCal helper and tidy code. Use it in LargeClusterMaker and also tidy this one

This might be useful also for the upgrade where we have to treat the FCAL0 like EME2 for eta > ~ 3.2 in view of ITK coverage

ping @llewitt and @jdevivi

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