[3.13] gh-61181: Fix support of choices with string value in argparse (GH-124578) (GH-124755)

Substrings of the specified string no longer considered valid values.
(cherry picked from commit f1a2417b9e2993e584610851ac004c8b0599b323)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
4 files changed