Add/navigation blocks post processing after migration from menu items (…

…#36950)

* add navigation.menuItemsToBlocks filter to postprocess blocks created from menu items

* Add navigation_after_parse_blocks_from_menu_items filter

* Make the filter experimental

* Lint

* Update menu-items-to-blocks.js

packages/block-library/src/navigation/menu-items-to-blocks.js

@@ -7,6 +7,7 @@ import { sortBy } from 'lodash';
  * WordPress dependencies
  */
 import { createBlock, parse } from '@wordpress/blocks';
+import { applyFilters } from '@wordpress/hooks';
 
 /**
  * Convert a flat menu item structure to a nested blocks structure.
@@ -21,7 +22,12 @@ export default function menuItemsToBlocks( menuItems ) {
 	}
 
 	const menuTree = createDataTree( menuItems );
-	return mapMenuItemsToBlocks( menuTree );
+	const blocks = mapMenuItemsToBlocks( menuTree );
+	return applyFilters(
+		'blocks.navigation.__unstableMenuItemsToBlocks',
+		blocks,
+		menuItems
+	);
 }
 
 /**