Ensure that full access to the sciml suite is available in python through diffeqpy & juliatorch

[LilithHafner]

This includes

• [x] solving differential equations
• [x] using autodiff to get gradients w.r.t. parameters and initial conditions
• [x] integrating with pytorch
• [ ] specifying custom autodiff backends (esp. Enzyme.jl)
• [ ] full integration with SciMLSensitivity

Meta tracking issue as requested by @joshday on Slack.