Replace #26850
Major changes:
1. Remove all `has` selectors, it is still not supported by firefox.
Actually there could be some more general and clearer approaches
2. Remove `two-toggle-buttons`, the `.ui.buttons` just works well
3. Rewrite the `.ui.buttons` border styles, see the screenshots
4. Remove the "fine-tuning" paddings from the the flex children, they
could layout themselves well.



