TrigT1CaloFexPerf: Adding Phase II ffex trigger EM algorithm

This MR adds a first implementation of Phase II fFEX EM trigger algorithms to the TrigT1CaloFexPerf package. fFEX electron objects are written and stored in the fEleCluster container. For now it is in the same LVL1 namespace as the Phase I algorithms.

The main steering class "FwdCellReader" runs the actual algorithm parts in "FFexEMFinder" relying on helper functions in the "FwdCell" class. The algorithm relies on cell level information.

A short overview of the actual algorithm and its variations can be found here: https://indico.cern.ch/event/958613/contributions/4047461/attachments/2130709/3588481/ffex_EM.pdf