Regression in accessibility since new buttons introduced

The buttons are actually focusable, just lacks some style to make that visible.

But at the same time, some improvements were indeed needed in terms of a11y:

• clicking any button, including "manag cookies", moved focus behind the popup - so I created separate buttons for manage / save preferences and move focus to first category switch when selecting "manage cookie"
• when category wrapper is revealed, tabindex on inputs is set to 0 - so I forced them back to -1 since we use the labels instead
• after tabbing through all categories it would make sense to have the "save preferences" button first - so I moved that to the top

Automatically closed - issue fixed for 2 weeks with no activity.