Issue #3411005: GitlabCI: Fix PHPCS and PHPStan validation errors

.gitlab-ci.yml

admin_toolbar.install

admin_toolbar.module

...ks_access_filter/admin_toolbar_links_access_filter.module

admin_toolbar_search/admin_toolbar_search.module

admin_toolbar_tools/src/Controller/ToolbarController.php

..._toolbar_tools/src/Form/AdminToolbarToolsSettingsForm.php

admin_toolbar_tools/src/Plugin/Derivative/ExtraLinks.php

admin_toolbar_tools/src/Plugin/Menu/MenuLinkEntity.php

src/Form/AdminToolbarSettingsForm.php

tests/src/Functional/AdminToolbarAdminMenuTest.php

tests/src/Functional/AdminToolbarAlterTest.php