Finish testing code examples in the docs (#25668)
Summary:
All of the code examples should now run as unit tests, save for those
that require interaction (i.e. show `pdb` usage) and those that use
CUDA.
`save` had to be moved before `load` in `jit/__init__.py` so `load`
could use the file generated by `save`
](https://our.intern.facebook.com/intern/diff/17192417/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25668
Pulled By: driazati
Differential Revision: D17192417
fbshipit-source-id: 931b310ae0c3d2cc6affeabccae5296f53fe42bc
