Make StateData polymorphic to support alternative state propagation equations

[juan-g-bonilla]

Describe your use case
So far, all states x in dynamic objects are represented by a matrix of some dimension m x n, with their derivatives x_dot being given by a matrix of the same dimensions, and first-order propagation forward in time expressed as:

x(t + Dt) = x(t) + Dt*x_dt(t)

However, we could benefit from enabling states that break this pattern. The state of a 3D rotation, for example, can be represented as a quaternion, which is represented by a 4x1 matrix. It's derivative, on the other hand, is an angular velocity of size 3x1. Integrating a quaternion forward in time given an angular velocity also uses a non-standard formula.

Describe alternatives solutions you've considered
I can't think of a way to support similar functionality without relying on hacky preprocessing/postprocessing around the integration functionality to express these special states into the standard format.

Additional context
This issue originally appeared when trying to support MuJoCo as a Basilisk module, whose joints make use of quaternions.

Interestingly, we could make use of this feature to improve how MRPs are handled in Basilisk:

class MRPStateData : public StateData
{
    void propagateState(double dt) override
    {
        super().propagateState(dt);
        // MRP switch here, if needed
    }
};

thus we let the special MRPStateData handle MRP switching and thus avoid having to implement this functionality on state effectors.