Editor: Automatically apply global styles duotone filters to render in post editor.

Global styles duotone filters were not rendering in the post editor. This fixes that by adding `wp_global_styles_render_svg_filters` to the `in_admin_header` so it renders in the body before the editor.

Follow-up [52757].

Props ajlende, abhanonstopnewsuk.
Fixes #55190.

git-svn-id: https://develop.svn.wordpress.org/trunk@52768 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/script-loader.php

@@ -2336,6 +2336,34 @@ function wp_enqueue_global_styles() {
 	wp_enqueue_style( 'global-styles' );
 }
 
+/**
+ * Render the SVG filters supplied by theme.json.
+ *
+ * Note that this doesn't render the per-block user-defined
+ * filters which are handled by wp_render_duotone_support,
+ * but it should be rendered before the filtered content
+ * in the body to satisfy Safari's rendering quirks.
+ *
+ * @since 5.9.1
+ */
+function wp_global_styles_render_svg_filters() {
+	/*
+	 * When calling via the in_admin_header action, we only want to render the
+	 * SVGs on block editor pages.
+	 */
+	if (
+		is_admin() &&
+		! get_current_screen()->is_block_editor()
+	) {
+		return;
+	}
+
+	$filters = wp_get_global_styles_svg_filters();
+	if ( ! empty( $filters ) ) {
+		echo $filters;
+	}
+}
+
 /**
  * Checks if the editor scripts and styles for all registered block types
  * should be enqueued on the current screen.