[md][freeflow] Update pressure and viscosity functions in couplingmanager

When using isRotationalExtrusion for a coupled momentum-mass problem, the coupling manager needs the functions effectiveViscosity(element, fvGeometry, scv) and pressure(element, fvGeometry, scv) (called by the base problem). These functions were missing.

Furthermore, the argument considerPreviousTimeStep has been added to these functions such that they are now consistent with the already implemented density functions.