feat: allow adding and deleting of items in submitted SO & PO (#19912)

* feat: allow adding of items after quotation submission

* feat: allow deletion of items from submitted SO & PO

* fix: case when items are added and deleted at once

* fix: add test cases
* For deletion of items while Updating Items after submitting PO & SO

erpnext/public/js/utils.js

@@ -458,7 +458,8 @@ erpnext.utils.update_child_items = function(opts) {
 					fieldname:"item_code",
 					options: 'Item',
 					in_list_view: 1,
-					read_only: 1,
+					read_only: 0,
+					disabled: 0,
 					label: __('Item Code')
 				}, {
 					fieldtype:'Float',