[3.13] gh-41872: Fix quick extraction of module docstrings from a file in pydoc (GH-127520) (GH-128620)

It now supports docstrings with single quotes, escape sequences,
raw string literals, and other Python syntax.

(cherry picked from commit 474e419792484d1c16e7d9c99b7bf144136b9307)

Co-authored-by: Srinivas Reddy Thatiparthy (తాటిపర్తి శ్రీనివాస్  రెడ్డి) <thatiparthysreenivas@gmail.com>
Co-authored-by: Éric <merwok@netwok.org>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>