typing: Document get_origin and get_args separately

[JelleZijlstra]

Currently get_args and get_origin share the same documentation paragraph:

This makes it look like get_args is undocumented. I think the two functions are different enough that it makes sense to give each its own paragraph of documentation.

Linked PRs

• gh-104010: Separate and improve docs for typing.get_origin and typing.get_args #104013
• [3.11] gh-104010: Separate and improve docs for typing.get_origin and typing.get_args (GH-104013) #104359

[chgnrdv]

Don't mind if I'll work on it? :)

[JelleZijlstra]

Go ahead!