Fix solution stripping for ODESolution

[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

Adds a test for stripping ODESolution objects of any function information.

[jClugstor]

It feels hacky to rely on typeof(sol).parameters to build the new ODESolution, but it seems it's needed?

[ChrisRackauckas]

This is not a good idea, it will not infer.

[ChrisRackauckas]

Instead use @set sol.interp = interp

[jClugstor]

Where does @set come from? When I do

 @set sol.interp = interp
   
    ODESolution(sol.u, sol.u_analytic, sol.errors,
        sol.t, sol.k, sol.discretes, nothing, nothing,
        sol.interp, sol.dense, sol.tslocation, sol.stats,
        sol.alg_choice, sol.retcode, sol.resid, sol.original)

It still gives a method error.

[jClugstor]

Would something like this be better?

N = sol.u === nothing ? 2 : ndims(eltype(sol.u)) + 1
T = eltype(eltype(sol.u))

[jClugstor]

Oh I see, from Accessors

[jClugstor]

Ok, this should be it now :-)