Set pd.options.display.max_columns=0 by default
Update: Remove everything related to `max_rows` and only deal with `max_columns` in this PR.

Changed `max_columns` to `0` (automatically adapt the number of displayed columns to the actual terminal width) when run in a terminal ~~and `max_rows` to `20` (because I'd like to see the "whole" data frame at a glance like in R's tibble)~~.

 - [x] closes #16579
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master -u -- "*.py" | flake8 --diff``
 - [x] whatsnew entry
