Bug 31754: Improve appearance of behavior of DataTables controls

Bug 31754: Improve appearance of behavior of DataTables controls

This patch makes changes to CSS and to the default DataTables DOM
configuration in order to make toolbars work better at various screen
widths.

The patch also makes stylelint corrections to _tables.scss.

To test, apply the patch and rebuild the staff interface CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

- Test pages in the staff interface where tables contain multiple pages
  of results, e.g. a patron search.
- Confirm that table information (entries) and controls look correct.
- Confirm that all controls work correctly, including the search field.
- Resize your browser to check how the controls respond at various
  browser widths.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>