hanconfig: add HLT muon subfolder structure based on L1 seed, automated with regexp

The purpose of this MR is to enable the automatic update in the monitoring of the L1 seed of single-muon chains from L1_MU14FCH to L1_MU18VFCH. Since histograms for many chains are defined in the monitoring, as configured here, it was needed to change the structure of the webdisplay histograms, adding subfolders corresponding to different L1 seeds. This MR implements these changes.

The impact on the structure of the webdisplay can be appreciated comparing the current webdisplay for run 451094 with the new version after this MR.

Tagging @okumura, and also @ebergeas for information (as we'll have to propagate this to T0 monitoring before the MU18 transition takes place).