fix/3773: custom order re-ordering for autosuggest

[Sidsector9]

Description of the Change

Closes #3773

Fixes Autosuggest custom result ordering when ep_autosuggest_query_args limits the number of displayed results.

When Custom Search Results is active, Autosuggest now fetches a larger result set so ordered posts beyond the display limit can still be repositioned correctly. The frontend then trims the reordered results back to the configured display limit.

How to test the Change

1. Go to ElasticPress > Custom Results and create a set of custom results.
2. Add the custom result at position 5, or change the order of the posts at positions 7 or 8
3. Set the number of results to 4 by using the ep_autosuggest_query_args filter.
4. Enable the Autosuggest feature.
5. Search for the term and compare the results.

Changelog Entry

Fixed - custom results order re-ordering for autosuggest

Credits

Props @burhandodhy @Sidsector9

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.