Issue #3400018 by mstrelan, xjm: Add declare(strict_types=1) to all Functional JavaScript tests

...unctionalJavascript/MaximumFileSizeExceededUploadTest.php

.../filter/tests/src/FunctionalJavascript/FilterHtmlTest.php

...e/tests/src/FunctionalJavascript/ImageAdminStylesTest.php

...age/tests/src/FunctionalJavascript/ImageFieldTestBase.php

...tests/src/FunctionalJavascript/ImageFieldValidateTest.php

...src/FunctionalJavascript/ImageFieldWidgetMultipleTest.php

...rc/FunctionalJavascript/FormErrorHandlerCKEditor5Test.php

..._builder/tests/src/FunctionalJavascript/AjaxBlockTest.php

...uilder/tests/src/FunctionalJavascript/BlockFilterTest.php

.../tests/src/FunctionalJavascript/BlockFormMessagesTest.php

...sts/src/FunctionalJavascript/ContentPreviewToggleTest.php

...er/tests/src/FunctionalJavascript/ContextualLinksTest.php

...builder/tests/src/FunctionalJavascript/FieldBlockTest.php

.../src/FunctionalJavascript/InlineBlockPrivateFilesTest.php

...uilder/tests/src/FunctionalJavascript/InlineBlockTest.php

...er/tests/src/FunctionalJavascript/InlineBlockTestBase.php

...sts/src/FunctionalJavascript/ItemLayoutFieldBlockTest.php

...tionalJavascript/LayoutBuilderDisableInteractionsTest.php

...rc/FunctionalJavascript/LayoutBuilderNestedFormUiTest.php

...tests/src/FunctionalJavascript/LayoutBuilderOptInTest.php