Removed the can_return_columns_from_insert skip gates on existing
field_defaults tests to confirm the expected number of queries are
performed and that returning field overrides are respected.
Raising DatabaseError directly made it harder than it should to
differentiate between IntegrityError when a forced update resulted in no
affected rows.
Introducing a specialized exception allows for callers to more easily
silence, log, or turn them update failures into user facing exceptions
(e.g. 404s).
Thanks Mariusz for the review.
The transitional logic added to deprecate the usage of *args for
Model.save()/asave() introduced two issues that this branch fixes:
* Passing extra positional arguments no longer raised TypeError.
* Passing a positional but empty update_fields would save all fields.
Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>
