[Active Record] Renamed private methods create_record and update_record

 This is to ensure that they are not accidentally called by the app code.
 They are renamed to _create_record and _update_record respectively.
 Closes #11645
Merge pull request #11650 from prathamesh-sonpatki/rename

Renamed private methods _create_record and _update_record
Add CHANGELOG entry for #11650 [ci skip]