[combo-box] Clarify filtering with dataProvider

[steverep]

Description

The [documentation for vaadin-combo-box](https://cdn.vaadin.com/vaadin-web-components/23.3.0-alpha2/#/elements/vaadin-combo-box) does not adequately describe how the params.filter` should affect the returned results. Basically there would be 2 options:

1. Apply the filter to the entire data set, then paginate the results, i.e. items always has a full page of results (except the last) and size is the total number of filtered results
2. Paginate the data set, then apply the filter to the requested page, i.e. size is the total number of unfiltered items and the returned items could be empty

I presume that option 1 is correct, but it would be nice if the docs were clearer. The example does not use params.filter so it also cannot be inferred from that.

Expected outcome

Clearer docs specifying one of the 2 options above.

Minimal reproducible example

n/a

Steps to reproduce

n/a

Environment

n/a

Browsers

No response

[steverep]

Along the same lines, also assume the page numbers start at 1, but nice to clarify.