Adding MDT residual+error plots to online muon monitoring (ATR-26365)

This MR is for the addition of two new plots in muon online monitoring, according to ATR-26365. I attach a preview based on the standard Trigger Validation EB input file: /cvmfs/atlas-nightlies.cern.ch/repo/data/data-art/TrigP1Test/data18_13TeV.00360026.physics_EnhancedBias.merge.RAW._lb0151._SFO-1._0001.1