Add a test that demonstrates the problem.
Instead of a visitor that will see all Projects, do an orderly search for the one that needs the cast.
Can now enable union-9, as both problems have been fixed.
merge MMcM: Be more selective about adding CAST to the top-level of an INSERT / UPDATE

Merge pull request #1177 from MMcM/sql-layer/sql-top-level-casting-not-visitor
https://github.com/FoundationDB/sql-layer/pull/1177