Adjust stepper interface and make it explicit through type trait assertions

This MR adds a surfaceReached method to the EigenStepper, StraightLineStepper and AtlasStepper. The function is aims towards the implementation of ACTS-541. The MR also starts fixing the interface of the steppers and their states by adding assertions in the Propagator and therewith the templated stepper in the propagation can be checked at compile time. This set also showed several missing parts in the AtlasStepper. With this MR its interface is fixed and the functions are reordered in all steppers to increase the readability.

Closes ACTS-462