[Autocomplete] Support for Virtual Scrolling/Pagination

[bendavies]

Hi,

Support for Virtual Scroll is included in the javascript: https://github.com/symfony/ux/blob/8e84d49a92b70f99001b8817cd3129a6215175f6/src/Autocomplete/assets/src/controller.ts#L131

But there is no support in the default php implmentation. Basically, the backend needs to support pagintion fo the data, returning a next_page item in the response, if there are more results.