sTGC: change the digits selection window to 8bc

At the present, L1 chain runs on sTGC RDO format, which uses 8 bc window, and sTGC DIGITS format has also updated the bcid conversionfrom [-1, 1] to [-3, 4]. To consider all hits within the new time window, the trigger simulation is updated accordingly now, following discussions in Jira: https://its.cern.ch/jira/browse/ATR-25612 @fgravili @chchau @masato @czodrows

(this is the first step, i guess there's still need the implemention of the narrower trigger capture window, and assigning the correct bcid to triggers with sliding time window logics, to be defined soon. fix the Jira's major bug firstly)