[multidomain][boundary][stokesdarcy] couplingmapper does not need couplingmanager
The couplingmapper could be simplified and not depend on the couplingmanager. The couplingmanager is only needed to get the FVGridgeometries in one function, which seems unnecessary.
What does this feature / why does DuMux need it: The dependency of the mapper on the couplingmanager create issues when trying to combine several couplingmangers. Removing that also means that the constructor of the couplingmanager can be removed, which is also nice and easier for inheritance.