ADTypes not exported by solver packages

[Ickaser]

Describe the bug 🐞
On master, with e.g.

using OrdinaryDiffEqRosenbrock
using OrdinaryDiffEqNonlinearSolve

at least the symbol AutoForwardDiff is not exported, which is part of the API for choosing autodiff I believe.
With

using OrdinaryDiffEq

the symbol is exported.

[oscardssmith]

we do want to be careful here. OrdinaryDiffEq exports way too much, but exporting a few options does seem reasonable. that said, if we are going to change the default autodiff to enzyme, it seems plausible that we don't want forwarddiff exported by default

[ChrisRackauckas]

I think in OrdinaryDiffEq v7 we should trim most of the dependencies and export only the basics.

[Ickaser]

OK, so going forward the API for choosing autodiff will involve explicitly importing ADTypes? Fine by me but should just get a note in the docs, probably

[ChrisRackauckas]

It would need to be noted, yes. I'm hoping we are getting pretty close to the point where that should be a rarity too 😅. I kind of want an auto auto that pre screens at compile time