ensure Bundle / DML RETURNING has test support, full impl

ensure Bundle / DML RETURNING has test support, full impl

Ensured the use case of :class:`.Bundle` objects used in the
``returning()`` portion of ORM-enabled INSERT, UPDATE and DELETE statements
is tested and works fully.   This was never explicitly implemented or
tested previously and did not work correctly in the 1.4 series; in the 2.0
series, ORM UPDATE/DELETE with WHERE criteria was missing an implementation
method preventing :class:`.Bundle` objects from working.

Fixes: #10776
Change-Id: I32298e65ac590a12b47dd6ba00b7d56038b8a450