Drop most convenience methods from pyflatsurf

[saraedum]

pyflatsurf adds some convenience methods to C++ objects, e.g., FlowDecomposition.cylinders() or FlatTriangulation.connections(). We should remove these methods in the current form because they will be very annoying to document (i.e., we cannot just point to the C++ documentation but have to write specific documentation for the Python interface here.)

Some of these methods should just exist on the C++ object, e.g., cylinders(), while others should be dropped, e.g., connections(); in the latter case we should make sure that it's easy to create the corresponding C++ object easily from Python.

Note that we don't need the added convenience that we initially planned here since everything is going to be wrapped in sage-flatsurf anyway. So ideally the C++ interface is is just an API that is not user facing.