Misc doc updates #2 (#24445)
Summary:
Another pass over the docs, this covers most of the remaining stuff
* content updates for new API
* adds links to functions instead of just names
* removes some useless indentations
* some more code examples + `testcode`s
](https://our.intern.facebook.com/intern/diff/16847964/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24445
Pulled By: driazati
Differential Revision: D16847964
fbshipit-source-id: cd0b403fe4a89802ce79289f7cf54ee0cea45073
