More efficient implementation of Hessian in FlatDyn.

Accept dxl as a template argument to avoid double differentiation.

Member smooth::feedback::MPC< T, X, U, F, CR, Kmesh, DT >::MPC (F &&f, CR &&cr, Eigen::Vector< double, Ncr > &&crl, Eigen::Vector< double, Ncr > &&cru, MPCParams &&prm={})

Optimization: The only time-dependent parts of the QP are the dynamics and end constraints, so only those need to be updated.

Member smooth::feedback::test_ocp_derivatives (OCPType auto &ocp, uint32_t num_trials=1, double eps=1e-4)

Make it possible to test a subset of derivatives