Allow specification of IK seed in Descartes Robot Sampler

[marip8]

Is your feature request related to a problem? Please describe.

tesseract_planning/tesseract_motion_planners/descartes/include/tesseract_motion_planners/descartes/impl/descartes_robot_sampler.hpp

Line 65 in 965e5e1

, ik_seed_(Eigen::VectorXd::Zero(dof_))

It appears that the IK seed for the Descartes robot sampler is set to all zeros by default. Solving IK with a seed of zero for robots whose all-zeros configuration is a singularity (e.g,. Franka FR3) fails for gradient based solvers like KDL. This in turn makes Descartes fail.

Describe the solution you'd like

• The RobotSampler class should accept an IK seed as an input argument (or give public access to it)
• DescartesDefaultPlanProfile::createWaypointSampler should attempt to set the IK seed using the input MoveInstruction

Describe alternatives you've considered

N/A

Additional context

See this issue for more context