Rework button focus/active styling, with extra changes for checks/radios (#37026)

Rework button focus/active styling, with extra changes for checks/radios (#37026)

* Replace :focus styles with :focus-visible

* Remove :active / .active styles

* Don't apply :hover styles for `.btn` that follows a `.btn-check`

This removes a large part of the visual confusion of button checks/radios - that you currently have to move your mouse away from them to see what they actually changed to (checked or unchecked)

* Reintroduce :active, but *not* for button checks/radios

* Sort focus styling specifically for button checks/radios

don't change background on focus, just give it the border/outline. again, avoids confusion whether something is checked or not while focused

* Re-add `outline:0` which was lost when resolving last merge conflict

Co-authored-by: Mark Otto <markd.otto@gmail.com>