Update gFEX input ByteStream decoder
With this MR the gFEX input ByteStream decoder is updated to include bug fixes and optimization. In particular:
- some maps for the transformation of gCaloTowers (readout input) into gTowers have been updated
- the type of towerEt in the gTower EDM has been changed (this shouldn't cause any type mismatch)
- Some details in the combination of the towers among the FPGAs have been updated