* Replace frappe.db.sql to frappe.get_list to apply permissions (#14037)
* Replace frappe.db.sql to frappe.get_list to apply permission
- All get_children method had frappe.db.sql in them which
had no permission check, now its replaced with frappe.get_list
which will check permission based on the user.
* Fix codacy
- Remove trailing whitespace
* Add parent filter
* Add ifnull checks