Master wrap muoncombinedconfig

This is the first step in wrapping the new Muon configuration in the existing configuration.

It isn't yet functional, and so is off by default (it is controlled by a new flag). I want to get it in now though to avoid collecting any more conflicts.

This MR includes some changes to the ComponentAccumulator. The reason for including it in this MR, is that this MR is the demonstration of why the changes are needed.

Finally, there are many tweaks to the new configuration, to fix problems and make the diff easier to manage when comparing old/new.