Removed versionadded and versionchanged for version prior to 1.2 since they
are no longer useful.

Change-Id: I5c53d1188bc5fec3ab4be39ef761650ed8fa6d3e

Change-Id: I625af65b3fb1815b1af17dc2ef47dd697fdc3fb1

Added new parameter :paramref:`.PoolEvents.reset.reset_state` parameter to
the :meth:`.PoolEvents.reset` event, with deprecation logic in place that
will continue to accept event hooks using the previous set of arguments.
This indicates various state information about how the reset is taking
place and is used to allow custom reset schemes to take place with full
context given.

Within this change a fix that's also backported to 1.4 is included which
re-enables the :meth:`.PoolEvents.reset` event to continue to take place
under all circumstances, including when :class:`.Connection` has already
"reset" the connection.

The two changes together allow custom reset schemes to be implemented using
the :meth:`.PoolEvents.reset` event, instead of the
:meth:`.PoolEvents.checkin` event (which continues to function as it always
has).

Change-Id: Ie17c4f55d02beb6f570b9de6b3044baffa7d6df6
Fixes: #8717

The :meth:`.DialectEvents.handle_error` event is now moved to the
:class:`.DialectEvents` suite from the :class:`.EngineEvents` suite, and
now participates in the connection pool "pre ping" event for those dialects
that make use of disconnect codes in order to detect if the database is
live. This allows end-user code to alter the state of "pre ping". Note that
this does not include dialects which contain a native "ping" method such as
that of psycopg2 or most MySQL dialects.

Fixes: #5648
Change-Id: I353d84a4f66f309d2467b7e67621db6b8c70411e

in this patch the asyncio/events.py module, which
existed only to raise errors when trying to attach event
listeners, is removed, as we were already coding an asyncio-specific
workaround in upstream Pool / Session to raise this error,
just moved the error out to the target and did the same thing
for Engine.

We also add an async_sessionmaker class.  The initial rationale
here is because sessionmaker() is hardcoded to Session subclasses,
and there's not a way to get the use case of
sessionmaker(class_=AsyncSession) to type correctly without changing
the sessionmaker() symbol itself to be a function and not a class,
which gets too complicated for what this is. Additionally,
_SessionClassMethods has only three methods on it, one of which
is not usable with asyncio (close_all()), the others
not generally used from the session class.

Change-Id: I064a5fa5d91cc8d5bbe9597437536e37b4e801fe

Change-Id: I42ed77f559e3ee5b8c600d98457ee37803ef0ea6

Fixed issues where a descriptive error message was not raised for some
classes of event listening with an async engine, which should instead be a
sync engine instance.

Change-Id: I00b9f4fe9373ef5fd5464fac10651cc4024f648e

also extends into some areas of utils, events and others
as needed.

Formalizes a public hierarchy for pool API,
with ManagesConnection -> PoolProxiedConnection /
ConnectionPoolEntry for connectionfairy / connectionrecord,
which are now what's exposed in the event API and other
APIs.  all public API docs moved to the new objects.

Corrects the mypy plugin's check for sqlalchemy-stubs
not being insatlled, which has to be imported using the
dash in the name to be effective.

Change-Id: I16c2cb43b2e840d28e70a015f370a768e70f3581

Change-Id: I49abf2607e0eb0623650efdf0091b1fb3db737ea

This is so that dialect methods that are called within init
can assume the same argument structure as when they are called
in other places; we can nail down the type of object as well.

This change seems to mostly impact the isolation level routines
in the dialects, as these are called during initialize()
as well as on established connections.  these methods can now
assume a non-proxied DBAPI connection object in all cases,
as it is commonly required that attributes like ".autocommit"
are set on the object which don't work well in a proxied
situation.

Other changes:

* adds an interface for the "connectionfairy" concept
  called PoolProxiedConnection.
* Removes ``Connectable`` superclass of Connection.
  ``Connectable`` was originally meant to provide for the
  "method which accepts connection or engine" theme.  As this
  pattern  is greatly reduced in 2.0 and Engine no longer extends
  from it, the ``Connectable`` superclass doesnt serve any real
  purpose.

Leading from that, to set this in I also applied pep 484 annotations
to the Dialect base, and then in the interests of seeing some
of the typing information show up in my IDE did a little bit for Engine,
Connection and others.  I hope that it's feasible that we can
add annotations to specific classes and attributes ahead of when we
actually try to mass-populate the whole library.  This was
the original spirit of pep-484 that we can apply annotations
gradually.  I do of course want to try to do a mass-populate
although i think even in that case we will end up doing a lot
of manual work anyway (in particular for the changes here which
are distinct from what the stubs have).

Fixes: #7122
Change-Id: I5dd7fbff8a7ae520a81c165091af12a6a68826db