Propagation state cannot be initialized outside the propagation

[andiwand]

Currently the propagation state which incorporated the navigator and stepper state cannot be initialized outside the propagation. This is not optimal for externalSurfaces in the Navigator or the list of surfaces in the DirectNavigator. Currently we hack our way around that by setting the state via code in the actor that only get executed once.

Listing some code consequences here:

• KalmanFitter external surface initialization https://github.com/acts-project/acts/blob/main/Core/include/Acts/TrackFitting/KalmanFitter.hpp#L377
• DirectNavigator initialization https://github.com/acts-project/acts/blob/main/Core/include/Acts/Propagator/DirectNavigator.hpp#L74

My proposed solution is to decouple the propagation state creation from the propagate call #2552

Apart from that it would be beneficial IMO to move some of the state properties or config properties into an option struct that is part of the PropagationOptions and can be set for each propagation individually.

[github-actions]

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