Autosave callbacks shouldn't be `after_save`

068f092ced8483e557725542dd919ab7c516e567 registered autosave callbacks
as `after_save` callbacks. This caused the regression described in #17209.

Autosave callbacks should be registered as `after_update` and
`after_create` callbacks, just like before.

This is a partial revert of 068f092ced8483e557725542dd919ab7c516e567.

Fixes #17209.