manufacture empty result for DELETE..RETURNING w/ no description

manufacture empty result for DELETE..RETURNING w/ no description

Established a workaround for what seems to be an intrinsic issue across
MySQL/MariaDB drivers where a RETURNING result for DELETE DML which returns
no rows using SQLAlchemy's "empty IN" criteria fails to provide a
cursor.description, which then yields result that returns no rows,
leading to regressions for the ORM that in the 2.0 series uses RETURNING
for bulk DELETE statements for the "synchronize session" feature. To
resolve, when the specific case of "no description when RETURNING was
given" is detected, an "empty result" with a correct cursor description is
generated and used in place of the non-working cursor.

Fixes: #10505
Change-Id: Ib56f1ec5746e2b3212e563169353bc023db84099