[3.11] gh-104010: Separate and improve docs for `typing.get_origin` and `typing.get_a...

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

* separate documentation and examples for both functions
* add examples demonstrating behaviour with unsupported types
* document return value of `get_origin` for `ParamSpecArgs` and `ParamSpecKwargs` instances

(cherry picked from commit a7a2dbbf72aceef61bfb50901bfa39bfb8d6d229)

Co-authored-by: chgnrdv <52372310+chgnrdv@users.noreply.github.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>