This patch adds a new checkbox to the print UI for two-sided printing.
The checkbox is only visible if the currently selected printer supports
two-sided printing.
Notable Changes:
- Add new section and checkbox for two-sided printing.
- Add new getter to settings proxy for supportsDuplex.
- Add new setter/getter to settings proxy for printDuplex.
- Add new test for no duplex with PDF printer.
- Add new test for toggle duplex in portrait orientation.
- Add new test for toggle duplex in landscape orientation.
- Add new test for toggle orientation with duplex checked.
- Correctly set duple mode in GTK print settings.
Depends on D94026
Differential Revision: https://phabricator.services.mozilla.com/D93621
d9f598b6bf