Demux Zero Suppression has side effects

In the demux zero suppression module, we use only the first 9 bits of the ET field, which is correct only for TAU and EGAMMA objects

https://gitlab.cern.ch/scouting-demonstrator/scouting-preprocessor/-/blob/master/components/data_reduction/firmware/hdl/zs_demux.vhd?ref_type=heads#L74-79

This might introduce side effects, in particular for the sums thresholds. During normal conditions, we have been running with >= 256 GeV threshold for the sums (basically > 511 in hw units), but:

511 = 0b111111111 = 0x1FF

namely 9 bits! So the sums thresholds are not doing anything. So, for instance, if all the other objects are below their relative threshold and the total ET is greater that 256 GeV, the BX would not be kept even though we would expect it to be kept.

Even worse, if all the objects are below thresholds and we have a jet of 256 GeV (512=0x200 in hw units), the BX would be suppressed (not expected as well).

The latter is a very unlikely case, but for the sums the effect is relevant