[ButtonBase] Better keyboard focused story

[oliviertassinari]

• The TypeScript definitions where assuming the classes object was cascading between the different elements. It does not! I took a strong implementation bias by not allowing it.
  The CSS is already cascading, having the same behavior for the classes property would have made debugging much harder. I believe I have fixed all the definitions cc @pelotom

Breaking change

• Rename the keyboardFocused feature focusVisible in order to follow the CSS specification wording:
  https://drafts.csswg.org/selectors-4/#the-focus-visible-pseudo
• Give up on the classes property to host the focus visible feature. The fact that the classes don't cascade was making it hard to use. Instead, we rely on a focusVisibleClassName property. This is allowing any component along the rendering chain to use the feature. For instance, a Switch component: Switch > SwitchBase > IconButton > ButtonBase.

<ButtonBase
- classes={{
-   keyboardFocused: 'my-class-name',
- }}
+ focusVisibleClassName="my-class-name"
/>

Closes #10976

[pelotom]

👍