[3.12] bpo-37755: Use configured output in pydoc instead of pager (GH-15105) (GH...

[3.12] bpo-37755: Use configured output in pydoc instead of pager (GH-15105) (GH-120262)

If the Helper() class was initialized with an output, the topics, keywords
and symbols help still use the pager instead of the output.
Change the behavior so  the output is used if available while keeping the
previous behavior if no output was configured.
(cherry picked from commit 2080425154d235b4b7dcc9a8a2f58e71769125ca)

Co-authored-by: Enrico Tröger <enrico.troeger@uvena.de>