MDL-71608 qbank_importquestions: Add importquestions to core

This implementation will introduce a qbank plugin "importquestions"
which will allow user to import a bank of questions in the question bank view
by replacing the core class. Having this plugin will give users
the flexibility of enabling or disabling the question import
in the question bank view.

Co-Authored-By: Marc-Alexandre <[email protected]>

lib/classes/plugin_manager.php

@@ -1939,7 +1939,7 @@ class core_plugin_manager {
             ),
 
             'qbank' => [
-                'deletequestion',
+                'deletequestion', 'importquestions',
             ],
 
             'qbehaviour' => array(