Update CR reco hist config writing

This addresses the issue brought up here: !48 (comment 4973576)

Write the full names of the CR histograms in the unfolding files, both in the unfolding_plots.yml and the unfolding_config.yml. This means they are also easily linked to each other. Note: now each selection has it's own CR plot entry, since the reco selection information is included in the plot name.

For dealing with the overflow issues brought up in the unfolding (https://gitlab.cern.ch/kcormier/uzh-ttbb-unfolding/-/merge_requests/18#note_4972727) I think that can now cleanly be handled their directly. For each observable (reco, aux, gen) the corresponding histogram can be looked up, and checked for overflow. Then we can apply the correct procedure separately to each axis depending on the observable.

Ideally it would be nice to make this more generic so the config doesn't 'know' about CR/aux, but just about which reco observables are used for each plot. On the other hand, since we aren't expected to make many more changes, I think moving forward with this is best for now.

example yaml outputs: unfolding_config.yml unfolding_plots.yml