Split btag_wps between nominal and extra wps
Follow up to !297 (merged)
Split btag working points between nominal one, to be used for configs requiring a single working point (b-jet pT calibration, tau-antitau b-jet aware overlap removal, bbyy + bbtt event selection...), and extra wps which can be used in addition if needed. Avoids assumption that first btag working point is used as the nominal one.