[random test failure] ResponsiveImageFieldUiTest::testResponsiveImageFormatterUi()

Problem/Motivation

ResponsiveImageFieldUiTest::testResponsiveImageFormatterUi() contains a race condition and will randomly fail.

Steps to reproduce

https://git.drupalcode.org/issue/drupal-3565152/-/jobs/7809827
https://git.drupalcode.org/project/drupal/-/merge_requests/6111/pipeline... (mentioned at #2829040-208: [meta] Known intermittent, random, and environment-specific test failures)

Proposed resolution

Before

    $page->pressButton('Save');
    $assert_session->responseContains("Select a responsive image style.");

After

    $page->pressButton('Save');
    $this->assertTrue($assert_session->waitForText('Select a responsive image style.'));

MR with the fix

https://git.drupalcode.org/project/drupal/-/merge_requests/14198
Repeat ResponsiveImageFieldUiTest 400x:
- https://git.drupalcode.org/issue/drupal-3565218/-/jobs/7813235
- All passed

MR without the fix

https://git.drupalcode.org/project/drupal/-/merge_requests/14199
Repeat ResponsiveImageFieldUiTest 400x:
- https://git.drupalcode.org/issue/drupal-3565218/-/jobs/7813257
- Failed 1 / 400

Remaining tasks

1. Review
2. RTBC
3. Commit
4. Rejoice

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet