Support for a new generic histogram scaling in the jet calibration sequence
This adds a new GenericHistScaleCorrection class, which is designed originally with the trigger-level dijet analysis in mind (where there is the need for an additional online --> offline calibration factor), but which can additionally be used also in other contexts as a generic way to insert another calibration step into the jet calibration chain.
For the moment, as there is only one use case, the code is aligned around the idea of a 1D histogram where the x-axis is pT, being applied to a jet where the pT is scaled to a new value. However, additional configuration options could be added to easily adjust this to also consider other histogram dimensionality, axis definitions, or methods for scaling the jet four-vector. These are not done at this time because it's not clear how much this is needed beyond the TLA, rather the code is designed to be more modular to support such extensions without too much additional effort.
This is associated with the calibration that was presented by @vnovik, and implements the functionality requested by the conveners during that approval. Here is a link to the talk in question: https://indico.cern.ch/event/985282/#5-zjet-balance-for-trigger-lev
Tagging @dmelini and @xingguo for the in situ subgroup