Better Solution to SplineXYZCoil in CoilSets

[dpanici]

Vectorize over knots and intervals instead of enforcing knots and intervals , but we need to make knots and intervals part of params possibly (in the compute function definition)

See curve winding surface PR (I think I do it somewhere in the compute fxns not the objective, but I did it in a way that is jax-differentiable), I think you can use get_params in the build method of the objective, then in the compute, update that params dict with the passed-in params dict, that way the non-optimizable params are present when computing the objective.