[migractions] add sanity check in rename_relation_type
If the relation is still present in the fs schema, we probably shouldn't
be renaming it (because it's still in use somewhere, possibly in a
different cube). Closes #3608172
change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')