defaults if otherwise unspecified; the limitation where non-
server column defaults aren't included in an INSERT FROM
SELECT is now lifted and these expressions are rendered as
constants into the SELECT statement.

CC goes from F to D

method :meth:`.Query.with_statement_hint` to support statement-level
hints that are not specific to a table.
fixes #3206

unify everything.
- create a new layer of separation between the "from order bys" and "column order bys",
so that an OVER doesn't ORDER BY a label in the same columns clause
- identify another issue with polymorphic for ref #3148, match on label
keys rather than the objects

The "anonymize label" logic is now generalized to ClauseAdapter, and takes
place when the anonymize_labels flag is sent, taking effect for all
.columns lookups as well as within traverse() calls against the label
directly.
- traverse() will also memoize what it gets in columns, so that
calling upon traverse() / .columns against the same Label will
produce the same anonymized label.  This is so that AliasedClass
produces the same anonymized label when it is accessed per-column
(e.g. SomeAlias.some_column) as well as when it is applied to a Query,
and within column loader strategies (e.g. query(SomeAlias)); the
former uses traverse() while the latter uses .columns
- AliasedClass now calls onto ColumnAdapter
- Query also makes sure to use that same ColumnAdapter from the AliasedClass
in all cases
- update the logic from 0.9 in #1068 to make use of the same
_label_resolve_dict we use for #2992, simplifying how that works
and adding support for new scenarios that were pretty broken
(see #3148, #3188)