gFEX MET updates

With this MR the simulation of the gFEX Jets without Jets algorithm is updated to obtain a real bitwise simulation of the firmware functionalities.

Additionally, the gFEX ByteStream decoder has been updated to properly save the MET information in the final EDM for the trigger object. In fact, I realized that the readout information was saved separately for each FPGA (as the information is provided in readout), while the TOB should contain the sum of the global quantities.

Note that the scalar quantities (SumEt and MET) are set to zero in the final EDM (both in simulation and in data) as the procedure for summing up the individual quantities is still under discussion.