[Autocomplete] Expand virtualized example to have grouped items

[Janpot]

• I have followed (at least) the PR section of the contributing guide.

Fixes #18597

I also tweaked the responsiveness a bit. There were some edge cases.

[mui-pr-bot]

No bundle size changes comparing c4c5a03...62f22b6

Generated by 🚫 dangerJS against 62f22b6

[oliviertassinari]

I have tried to handle the height issue + the 8px padding on the top and bottom. Let me know what you think about it, I believe we are good :).

[Janpot]

👍 I guess that would work. What abut a constant to avoid the magic numbers? Like:

const LISTBOX_PADDING = 8;
// ...
top: style.top + LISTBOX_PADDING
// ...
height={getHeight() + 2 * LISTBOX_PADDING}

[oliviertassinari]

Sure 👍

[oliviertassinari]

Thank you