Load structured data blocks assets in site editor

* Change enqueue method to newer `enqueue_block_assets`. This also affects the frontend, which we do not want, hence the `is_admin` check
* Add styling dependencies on `dashicons` and `forms`, these are missing in the site editor: not sure if a WP components bug, but this solves it
* Add fieldset (`.schema-how-to-duration`) styling (copied from WP common), removing the border around the duration

admin/class-admin-asset-manager.php

@@ -635,7 +635,11 @@ protected function styles_to_be_registered() {
 			[
 				'name' => 'structured-data-blocks',
 				'src'  => 'structured-data-blocks-' . $flat_version,
-				'deps' => [ 'wp-edit-blocks' ],
+				'deps' => [
+					'dashicons',
+					'forms',
+					'wp-edit-blocks',
+				],
 			],
 			[
 				'name' => 'elementor',

src/integrations/blocks/structured-data-blocks.php

@@ -69,7 +69,7 @@ public function __construct(
 	 * @return void
 	 */
 	public function register_hooks() {
-		\add_action( 'enqueue_block_editor_assets', [ $this, 'enqueue_block_editor_assets' ] );
+		\add_action( 'enqueue_block_assets', [ $this, 'enqueue_block_editor_assets' ] );
 		$this->register_blocks();
 	}
 
@@ -148,6 +148,11 @@ public function register_blocks() {
 	 * @return void
 	 */
 	public function enqueue_block_editor_assets() {
+		// Bail if not in the admin.
+		if ( ! \is_admin() ) {
+			return;
+		}
+
 		/**
 		 * Filter: 'wpseo_enable_structured_data_blocks' - Allows disabling Yoast's schema blocks entirely.
 		 *