Move simulation code to subpackage

[dweindl]

Move simulation code to subpackages under amici.sim, amici.simulation, amici.simulations or similar, Don't import the amici extension by default.

For example, everything related to the swig interface can go to amici.simulation.sundials, petab+sundials functionality to amici.simulation.sundials.petab, amici.simulation.sundials.petab.v1.
Similar for amici.simulation.jax, amici.simulation.jax.petab.

• Wait for Move amici.petab to amici.importers.petab #3039
• Move code related to sundials-based simulation to amici.sim.sundials
• Move code related to simulating jax-based models to amici.sim.jax (after update of JAX-PEtab code)
• move simulation related code from amici.importers.petab to amici.sim.sundials (started in Move petab v1 simulation code to amici.sim... #3086)
  • petab v2 (Move petab v2 simulation code to amici.sim #3093)
  • parameter mapping
  • amici.debug (Move amici.debug #3091)