Add functional test for media library appearance after filtering and paging

Problem/Motivation

Changes to address 🐛 ajax_page_state leaks through request in Views Ajax Needs work affect properties in ajax_page_state, which has surfaced some test coverage gaps such as theme negotiation in AJAX requests for media library. A test was added for generic AJAX view case to catch theme negotiation regressions, but this is a follow up to add a specific test to catch any future media library theme negotiation regression as described in https://www.drupal.org/project/drupal/issues/3399951#comment-15333415 🐛 ajax_page_state leaks through request in Views Ajax Needs work

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet