dev/core#2312 SearchKit - Improve results loading time in admin UI

[colemanw]

Overview

Per https://lab.civicrm.org/dev/core/-/issues/2312 this separates the ajax calls for fetching search results & the pager count for a snappier UX.

This addresses the issue on the admin screen but not yet for search displays, which need reworking anyway to go through a permissioned wrapper api.

Before

Single api call for rows & count might be very slow.

After

Fetch a page of results before loading pager count for asynchronous speed.

[civibot]

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[eileenmcnaughton]

Thank you - this will improve the impression of it not working when the count request is slow