Delete old scripts and transfer relevant logic to tests and tutorials

[orionarcher]

Currently the /examples/scripts directory contains substantial use of unbatched integrators and old usage patterns. These should either be simplified and turned into tutorials, cleaned up and refactored for readability, or deleted.

If we end up with a large number of readable scripts that are not tutorials, we can host these on the docs.

The /examples/scripts/readme.md file should be updated when this is complete.

[janosh]

@orionarcher does removal of the unbatched code in #206 address this issue?

in some of the last commits in that PR, i refactored any code in npt.py, nvt.py and a2c.py that didn't support a batch dimension / made assumptions on tensor shapes that broke when having batches. i haven't actually run any batched NPT yet but i think it might be possible now