Systematics management cleanup

For ease of review, the more bread-and-butter changes have been externalized to this MR: !699 (merged)

Release notes

Systematics management has been refactored significantly

• New class TQSystematicsManager makes systematics management from SFramework now available in QFramework
• TSModelBuilder now uses TQSystematicsManager
• TQSystematicsHandler (aka yellow band factory) now also uses TQSystematicsManager

This achieves the ability to (for the first time) have a completely coherent implementation of systematic uncertainties for pre- and postfit.

Details

This MR contains several major types of changes:

• Old legacy code from SFramework has been removed. This mostly affects the (now removed) TSHWWUtils as well as the (significantly slimmed down) ActionCreateModels
• SFramework unit tests have been made a lot more restrictive by propagating escape codes of actions to the TSStatisticsManager
• const correctness has been improved throughout TQHistogramUtils
• code has been moved from SFramework to QFramework (TSSystematicsManager -> TQSystematicsManager, new class TSSystematicsManager inherits from `TQSystematicsManager and adds a few wrapper functions for compatibility)
• TQSystematicsHandler (aka the yellow band maker) has been completely rewritten and now uses TQSystematicsManager as a backend.

The major achievements of this MR include:

• significant reduction in code duplication
• removal of dead code
• speedup of yellow band making
• implementation of advanced variation computations in yellow band maker

This MR is part of the "histogramming harmonization" effort.