hardening against inappropriate multi-table updates

hardening against inappropriate multi-table updates

Hardening of the compiler's actions for UPDATE statements that access
multiple tables to report more specifically when tables or aliases are
referenced in the SET clause; on cases where the backend does not support
secondary tables in the SET clause, an explicit error is raised, and on the
MySQL or similar backends that support such a SET clause, more specific
checking for not-properly-included tables is performed.  Overall the change
is preventing these erroneous forms of UPDATE statements from being
compiled, whereas previously it was relied on the database to raise an
error, which was not always guaranteed to happen, or to be non-ambiguous,
due to cases where the parent table included the same column name as the
secondary table column being updated.

Fixed bug where the ORM would pull in the wrong column into an UPDATE when
a key name inside of the :meth:`.ValuesBase.values` method could be located
from an ORM entity mentioned in the statement, but where that ORM entity
was not the actual table that the statement was inserting or updating.  An
extra check for this edge case is added to avoid this problem.

Fixes: #12692
Change-Id: I342832b09dda7ed494caaad0cbb81b93fc10fe18