Feature request: change instance constraints without rebuilding entire problem

[Peter230655]

I believe at present opty does not support to change instance constraints, without setting up Problem again.
With some simulations it helps convergence if one starts with a simpler problem and use the solution of it as initial guess of a more difficult problem. The more difficult problem often has different instance constraints.

It would be convenient if instance constraints could be changed (similar to par_map) without setting up Problem again.

[moorepants]

This should be possible given that instance constraints are built separately from the equation of motion constraints. It is a matter of identifying all the unique steps to building the instance constraints functions, separating them from the eom constraint code, and then making sure that if you update them the steps are run fully and in order.