Create a filter for image style list page.

1. Fixed test issues -- (Updated `ImageStyleListBuilder.php`);
2. Added test case to `ImageAdminStylesTest.php`;

For the new service a change record will be needed.

Also D10 is not using es6 so

+ * DO NOT EDIT THIS FILE.
+ * See the following change record for more information,
+ * https://www.drupal.org/node/2815083 →
+ * @preserve
+ */

Doesn't apply.

Also patch seems to contain a ton of reformatting in the tests that seems out of scope for this issue and should be reverted.

Thank you @smustgrave

I'm currently creating change record for the issue.

A link to the change record: Added filter for the image styles on the image style list page →
Please review.

1. Removed useless comment regarding ES6 from the js file.
2. Reverted formatting code changes from the test file.

+++ b/core/modules/image/tests/src/Functional/ImageAdminStylesTest.php
@@ -298,6 +298,15 @@ class ImageAdminStylesTest extends ImageFieldTestBase {
+    // Test if search image style form exists.
+    $this->drupalGet($admin_path);
+    $image_styles = ImageStyle::loadMultiple();
+    $xpath = '//input[@placeholder="Filter by style name"]';
+    if (count($image_styles) > 1) {
+      $this->assertSession()
+        ->elementExists('xpath', $xpath);
+    }
+

It could be good to move this to a dedicated FunctionalJavascript test and test that the actual filtering works. ModuleFilterTest might be a good example to use