sTGC Strip Trigger: implement the physical cluster formation logics with adjacent strips in the same layer

Previously, the code gathered strips from all sectors, then just used one strip digit as a cluster to prevent the wrong usage of channelID, due to which only has the distingush power within the same layer

Now the layer divided logic is implemented for the gathered strips, hence the physical cluster could be formed with adjacent strips using channelId (+-1), which is expected to solve the cluster_Y resolution problems, reported in slides 15:

https://indico.cern.ch/event/1128868/contributions/4789388/attachments/2411428/4126440/2022-03-18%20sTGC%20Trigger%20Simulation%20%28Overlay%29.pdf

thanks for help from @fgravili ./ccing @rosati @iodice @vadamico