Integrate the layout tree into the monitoring suite

Description

Currently, the monitoring suite is built very statically, using numbers in a JSON file (gemmonitor/html/json/monitorables.json) which may not be correct for GE2/1 and ME0. All of this information is stored in the layout tree and should be accessible, ala !252 (merged) which grabs the OH information from the layout tree.

Further, since the layout tree is used to setup the full DAQ codebase, this contains the information of the specific parts of the detector in use. This means the monitor table could more dynamically be created, e.g. only display OHs in use in the table rather than all 12 columns regardless of the AMC. This is mentioned in this discussion. !252 (comment 5453270)