Cleanup documentation around `script` and `trace` (#24208)
Summary:
Stacked PRs
* #24258 - [jit] Add `trace_module` to docs
* **#24208 - [jit] Cleanup documentation around `script` and `trace`**
Examples / info was duplicated between `ScriptModule`, `script`, and
`trace`, so this PR consolidates it and moves some things around to make
the docs more clear.
For reviewers, if you want to see the rendered output, ping me for a
link
](https://our.intern.facebook.com/intern/diff/16746236/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24208
Pulled By: driazati
Differential Revision: D16746236
fbshipit-source-id: fac3c6e762a31c897b132b8421baa8d4d61f694c
