Add support for ScalarNonlinearFunction.

[stephanmg]

Hi,
thanks first for the nice package.

I tried to set up a simple MINLP by the help of the README, but it fails with the following error message:
ERROR: LoadError: The solver does not support an objective function of type MathOptInterface.ScalarNonlinearFunction.

Any idea?

[odow]

I transferred this issue to Pavtio. We do to support the new nonlinear interface to JuMP yet. You need to use the legacy nonlinear interface https://jump.dev/JuMP.jl/stable/manual/nlp/.

Question also asked on https://discourse.julialang.org/t/jump-with-pajarito-pavito-for-a-simple-minlp-fails-with-solver-does-not-support-mathoptinterface-scalarnonlinearfunction/106314