MDL-74465 blocks: allow configuration in modal

Introduce 'pagehash' - an identifier that uniquely identifies a page for the user session

lib/navigationlib.php

@@ -4230,7 +4230,7 @@ class flat_navigation extends navigation_node_collection {
             $addblockurl = "?{$url->get_query_string(false)}";
 
             $PAGE->requires->js_call_amd('core/addblockmodal', 'init',
-                [$PAGE->pagetype, $PAGE->pagelayout, $addblockurl]);
+                [$addblockurl, $this->page->get_edited_page_hash()]);
         }
     }