Fix usage of :option: in the docs (#9312).

Fix usage of :option: in the docs (#9312).

:option: is used to create a link to an option of python, not to mark
up any instance of any arbitrary command-line option.  These were
changed to ````.

For modules which do have a command-line interface, lists of options
have been properly marked up with the program/cmdoption directives
combo.  Options defined in such blocks can be linked to with :option:
later in the same file, they won’t link to an option of python.

Finally, the markup of command-line fragments in optparse.rst has
been cleaned to use ``x`` instead of ``"x"``, keeping that latter
form for actual Python strings.

Patch by Eli Bendersky and Éric Araujo.