Adjusted the SQL compilation for string containment functions
``.contains()``, ``.startswith()``, ``.endswith()`` to force the use of the
string concatenation operator, rather than relying upon the overload of the
addition operator, so that non-standard use of these operators with for
example bytestrings still produces string concatenation operators.

To accommodate this, needed to add a new _rconcat operator function,
which is private, as well as a fallback in concat_op() that works
similarly to Python builtin ops.

Fixes: #8253
Change-Id: I2b7f56492f765742d88cb2a7834ded6a2892bd7e
(cherry picked from commit 85a88df13ab8d217331cf98392544a888b4d7df3)

Fixed an issue where using :func:`.bindparam` with no explicit data or type
given could be coerced into the incorrect type when used in expressions
such as when using :meth:`.ARRAY.comparator.any` and
:meth:`.ARRAY.comparator.all`.

Fixes: #7979
Change-Id: If7779e713c9a3a5fee496b66e417cfd3fca5b1f9
(cherry picked from commit 889cbe53121c8fd50c845357dd52b24594346b68)

Fixed bug in :class:`.ARRAY` datatype in combination with :class:`.Enum` on
PostgreSQL where using the ``.any()`` method to render SQL ANY(), given
members of the Python enumeration as arguments, would produce a type
adaptation failure on all drivers.

Fixes: #6515
Change-Id: Ia1e3b4e10aaf264ed436ce6030d105fc60023433
(cherry picked from commit d023c8e1c7ad82fb249fab5155eb83dee17a160c)

Improvements to the test suite's integration with pytest such that the
"warnings" plugin, if manually enabled, will not interfere with the test
suite, such that third parties can enable the warnings plugin or make use
of the ``-W`` parameter and SQLAlchemy's test suite will continue to pass.
Additionally, modernized the detection of the "pytest-xdist" plugin so that
plugins can be globally disabled using PYTEST_DISABLE_PLUGIN_AUTOLOAD=1
without breaking the test suite if xdist were still installed. Warning
filters that promote deprecation warnings to errors are now localized to
SQLAlchemy-specific warnings, or within SQLAlchemy-specific sources for
general Python deprecation warnings, so that non-SQLAlchemy deprecation
warnings emitted from pytest plugins should also not impact the test suite.

Identified a bit of cleanup for the PostgreSQL provisioning
as a result.

Fixes: #7599
Change-Id: Ibcf09af25228d39ee5a943fda82d8a9302433726
(cherry picked from commit a0f1914b903de6c130ab1c3267138b8ad208e144)

This patch adds new warnings for all elements that
don't indicate their caching behavior, including user-defined
ClauseElement subclasses and third party dialects.
it additionally adds new documentation to discuss an apparent
performance degradation in 1.4 when caching is disabled as a
result in the significant expense incurred by ORM
lazy loaders, which in 1.3 used BakedQuery so were actually
cached.

As a result of adding the warnings, a fair degree of
lesser used SQL expression objects identified that they did not
define caching behavior so would have been producing
``[no key]``, including PostgreSQL constructs ``hstore``
and ``array``.  These have been amended to use inherit
cache where appropriate.  "on conflict" constructs in
PostgreSQL, MySQL, SQLite still explicitly don't generate
a cache key at this time.

The change also adds a test for all constructs via
assert_compile() to assert they will not generate cache
warnings.

Fixes: #7394
Change-Id: I85958affbb99bfad0f5efa21bc8f2a95e7e46981
(cherry picked from commit 22deafe15289d2be55682e1632016004b02b62c0)

Adjusted the compiler's generation of "post compile" symbols including
those used for "expanding IN" as well as for the "schema translate map" to
not be based directly on plain bracketed strings with underscores, as this
conflicts directly with SQL Server's quoting format of also using brackets,
which produces false matches when the compiler replaces "post compile" and
"schema translate" symbols. The issue created easy to reproduce examples
both with the :meth:`.Inspector.get_schema_names` method when used in
conjunction with the
:paramref:`_engine.Connection.execution_options.schema_translate_map`
feature, as well in the unlikely case that a symbol overlapping with the
internal name "POSTCOMPILE" would be used with a feature like "expanding
in".

Fixes: #7300
Change-Id: I6255c850b140522a4aba95085216d0bca18ce230
(cherry picked from commit b919a0a85afd5066f9188b20ef06ee1b4af884a9)

Fixed an inconsistency in the any_() / all_() functions / methods where the
special behavior these functions have of "flipping" the expression such
that the "ANY" / "ALL" expression is always on the right side would not
function if the comparison were against the None value, that is,
"column.any_() == None" should produce the same SQL expression as "null()
== column.any_()". Added more docs to clarify this as well, plus mentions
that any_() / all_() generally supersede the ARRAY version "any()" /
"all()".

Fixes: #7140
Change-Id: Ia5d55414ba40eb3fbda3598931fdd24c9b4a4411

Change-Id: I306cfbea9920b35100e3087dcc21d7ffa6c39c55

Change-Id: I488c9557eda390e4a88319affd4c8813ee274f80

Adjusted the logic added as part of :ticket:`6397` in 1.4.12 so that
internal mutation of the :class:`.BindParameter` object occurs within the
clause construction phase as it did before, rather than in the compilation
phase. In the latter case, the mutation still produced side effects against
the incoming construct and additionally could potentially interfere with
other internal mutation routines.

In order to solve the issue of the correct operator being present
on the BindParameter.expand_op, we necessarily have to expand the
BinaryExpression._negate() routine to flip the operator on the
BindParameter also.

Fixes: #6460
Change-Id: I1e53a9aeee4de4fc11af51d7593431532731561b