BTaggingSelectionTool: f_tau for CTagging in Continuous2D scheme [https://its.cern.ch/jira/browse/AFT-756] + more robust bad configs checks
This Merge Request addresses the issue of having distinct tau fractions for b- and c-tagging. Previously, the selection tool in the Continuous2D scheme did not account for this difference, evaluating the tagger discriminant using the same f_tau value for both b- and c-tagging. With this update, the tool can now access and utilize separate tau fraction values when running in this configuration.