Fix interpolation for stripped solutions

[jClugstor]

Checklist

• [x ] Appropriate tests were added
• [x ] Any code changes were done in a way that does not break public API
• [x ] All documentation related to code changes were updated
• [x ] The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• [x ] Any new documentation only uses public API

Additional context

Fixes interpolation for stripped solution objects, i.e. solution objects from strip_solution.

I'm not sure about doing struct ODENullFunction <: SciMLBase.AbstractODEFunction{false} end, but the inner constructor for ODEProblem doesn't allow f to be nothing. And the alternative seems to be changing the functors for ODEProblem. This also allows for stripped_solutions to keep some problem information. It might be good to add taking out the whole problem as an option as well?