Use L0Conf instead of DecodersDB to set up decoding of L0Report

Following the removal of L0 decoding by default in Brunel (Brunel!482 (merged)), the brunel.2016magup-oldrich test was printing

ToolSvc.L0DUConfig  ERROR L0DUMultiConfigProvider:: The requested TCK = 0x1609 is not registered  [L0DUFromRaw]
L0DUFromRaw.L0D...WARNING L0DUFromRawTool::  Unable to load the configuration for tck = 0x1609 --> Incomplete L0DUReport

at every event, due to incomplete setup of the L0 decoding by the Rich monitoring. This MR fixes this issue.

@jonrob FYI. I was surprised that the brunel.2016magup-oldrich test was the only one to fail in this way. It means that neither L1SizeMonitoring nor HPDHitPlots are enabled in any of the more modern Brunel tests.