Start using ADTypes rather than Bool for autodiff

[visr]

I noticed in the test logs a new deprecation warning:

┌ Warning: Using a `Bool` for keyword argument `autodiff` is deprecated. Please use an `ADType` specifier.
│   caller = _process_AD_choice(ad_alg::Bool, chunksize::Val{0}, diff_type::Val{:forward}) at misc_utils.jl:147
└ @ OrdinaryDiffEqCore ~/.julia/packages/OrdinaryDiffEqCore/33WQj/src/misc_utils.jl:147

See https://github.com/SciML/ADTypes.jl.
In our config we have autodiff = true/false. I guess we'd keep that for now and just map true to AutoForwardDiff.