HasPrefix / HasSuffixes / SupportsCloneAnnotations exported
a _traverse_internals attribute that does not represent a
complete traversal, meaning non-traversible subclasses would
seem traversible.  rename these attributes so that this
does not occur.  DML is currently not traversible (will be soon).

Change-Id: I2605e61c8c3d49965335e66e09f4aeedc5e73bd3

Change-Id: I08440dc25e40ea1ccea1778f6ee9e28a00808235

Added test support and repaired a wide variety of unnecessary reference
cycles created for short-lived objects, mostly in the area of ORM queries.

Fixes: #5056
Change-Id: Ifd93856eba550483f95f9ae63d49f36ab068b85a

Added one traversal test, callcounts have been brought from 29754 to
5173 so far.

Change-Id: I164e9831600709ee214c1379bb215fdad73b39aa

Created new visitor system called "internal traversal" that
applies a data driven approach to the concept of a class that
defines its own traversal steps, in contrast to the existing
style of traversal now known as "external traversal" where
the visitor class defines the traversal, i.e. the SQLCompiler.

The internal traversal system now implements get_children(),
_copy_internals(), compare() and _cache_key() for most Core elements.
Core elements with special needs like Select still implement
some of these methods directly however most of these methods
are no longer explicitly implemented.

The data-driven system is also applied to ORM elements that
take part in SQL expressions so that these objects, like mappers,
aliasedclass, query options, etc. can all participate in the
cache key process.

Still not considered is that this approach to defining traversibility
will be used to create some kind of generic introspection system
that works across Core / ORM.  It's also not clear if
real statement caching using the _cache_key() method is feasible,
if it is shown that running _cache_key() is nearly as expensive as
compiling in any case.    Because it is data driven, it is more
straightforward to optimize using inlined code, as is the case now,
as well as potentially using C code to speed it up.

In addition, the caching sytem now accommodates for anonymous
name labels, which is essential so that constructs which have
anonymous labels can be cacheable, that is, their position
within a statement in relation to other anonymous names causes
them to generate an integer counter relative to that construct
which will be the same every time.   Gathering of bound parameters
from any cache key generation is also now required as there is
no use case for a cache key that does not extract bound parameter
values.

Applies-to: #4639
Change-Id: I0660584def8627cad566719ee98d3be045db4b8d

Added new entity-targeting capabilities to the :class:`.Query` object to
help with the case where the :class:`.Session` is using a bind dictionary
against mapped classes, rather than a single bind, and the :class:`.Query`
is against a Core statement that was ultimately generated from a method
such as :meth:`.Query.subquery`; a deep search is performed to locate
any ORM entity related to the query in order to locate a mapper if
one is not otherwise present.

Fixes: #4829
Change-Id: I95cf325a5aba21baec4b313246c6f4d692284820

Change-Id: I6a71f4924d046cf306961c58dffccf21e9c03911

Applied on top of a pure run of black -l 79 in
I7eda77fed3d8e73df84b3651fd6cfcfe858d4dc9,  this set of changes
resolves all remaining flake8 conditions for those codes
we have enabled in setup.cfg.

Included are resolutions for all remaining flake8 issues
including shadowed builtins, long lines, import order, unused
imports, duplicate imports, and docstring issues.

Change-Id: I4f72d3ba1380dd601610ff80b8fb06a2aff8b0fe

This is a straight reformat run using black as is, with no edits
applied at all.

The black run will format code consistently, however in
some cases that are prevalent in SQLAlchemy code it produces
too-long lines.   The too-long lines will be resolved in the
following commit that will resolve all remaining flake8 issues
including shadowed builtins, long lines, import order, unused
imports, duplicate imports, and docstring issues.

Change-Id: I7eda77fed3d8e73df84b3651fd6cfcfe858d4dc9

Change-Id: I3ef36bfd0cb0ba62b3123c8cf92370a43156cf8f