- move out logging tests from test_execute to test_logging

Leave this test in place as its ultimately a SQLite use case, but only test on SQLite.
We perhaps should add another test case that works on all platforms.

implemented right before the release of 0.9.3 affected the case where
a UNION contained nested joins in it.   "Join rewriting" is a feature
with a wide range of possibilities and is the first intricate
"SQL rewriting" feature we've introduced in years, so we're sort of
going through a lot of iterations with it (not unlike eager loading
back in the 0.2/0.3 series, polymorphic loading in 0.4/0.5). We should
be there soon so thanks for bearing with us :).
fixes #2969   re: #2967
- solve the issue of join rewriting inspecting various types of
from objects without using isinstance(), by adding some new
underscored inspection flags to the FromClause hierarchy.

on the columns clause of the SELECT statement if the targets were
aliased tables, as opposed to individual aliased columns.

would fail to be rewritten properly, such as when the exists is
mapped to a column_property in an intricate nested-join scenario. #2967

:ticket:`2369` and :ticket:`2587` where a nested join with one side
already an aliased select would fail to translate the ON clause on the
outside correctly; in the ORM this could be seen when using a
SELECT statement as a "secondary" table. [ticket:2858]

are transferred correctly for when .key is present; tests have been enhanced
to test this condition for render, result map construction, statement
execution.  [ticket:2790]

- fix the result map rewriter for col mismatches, since the rewritten
select at the moment typically has more columns than the original

the joins as is, regardless of the dialect not supporting it.  use_labels=True
indicates a higher level of automation and also can maintain the labels
between rewritten and not.  use_labels=False indicates a manual use case.