try to get file naming to be more sane for pysqlite file databases

Change-Id: I68ad8c2f6c6c25930fbffdd79b8d429cd7a7dd9a

The support for pool ping listeners to receive exception events via the
:meth:`.ConnectionEvents.handle_error` event added in 2.0.0b1 for
:ticket:`5648` failed to take into account dialect-specific ping routines
such as that of MySQL and PostgreSQL. The dialect feature has been reworked
so that all dialects participate within event handling.   Additionally,
a new boolean element :attr:`.ExceptionContext.is_pre_ping` is added
which identifies if this operation is occurring within the pre-ping
operation.

For this release, third party dialects which implement a custom
:meth:`_engine.Dialect.do_ping` method can opt in to the newly improved
behavior by having their method no longer catch exceptions or check
exceptions for "is_disconnect", instead just propagating all exceptions
outwards. Checking the exception for "is_disconnect" is now done by an
enclosing method on the default dialect, which ensures that the event hook
is invoked for all exception scenarios before testing the exception as a
"disconnect" exception. If an existing ``do_ping()`` method continues to
catch exceptions and check "is_disconnect", it will continue to work as it
did previously, but ``handle_error`` hooks will not have access to the
exception if it isn't propagated outwards.

Fixes: #5648
Change-Id: I6535d5cb389e1a761aad8c37cfeb332c548b876d

Change-Id: I625af65b3fb1815b1af17dc2ef47dd697fdc3fb1

command run is "pyupgrade --py37-plus --keep-runtime-typing --keep-percent-format <files...>"
pyupgrade will change assert_ to assertTrue. That was reverted since assertTrue does not
exists in sqlalchemy fixtures

Change-Id: Ie1ed2675c7b11d893d78e028aad0d1576baebb55

to simplify pyproject.toml change the remaining files
that aren't going to be typed on this first pass
(unless of course someone wants to type some of these)
to include # mypy: ignore-errors.   for the moment, only a handful
of ORM modules are to have more type checking implemented.

It's important that ignore-errors is used and
not "# type: ignore", as in the latter case, mypy doesn't even
read the existing types in the file, which makes it impossible to
type any files that refer to those modules at all.

to simplify ongoing typing work use inline mypy config
for remaining files that are "done" for now, indicating the
level of type checking they currently have.

Change-Id: I98669c1a305c2f0adba85d10b5425541f3fe9533

the pep484 task becomes more intense as there is mounting
pressure to come up with a consistency in how data moves
from end-user to instance variable.

current thinking is coming into:

1. there are _typing._XYZArgument objects that represent "what the
   user sent"
2. there's the roles, which represent a kind of "filter" for different
   kinds of objects.   These are mostly important as the argument
   we pass to coerce().
3. there's the thing that coerce() returns, which should be what the
   construct uses as its internal representation of the thing.
   This is _typing._XYZElement.

but there's some controversy over whether or
not we should pass actual ClauseElements around by their role
or not.   I think we shouldn't at the moment, but this makes the
"role-ness" of something a little less portable. Like, we have
to set DMLTableRole for TableClause, Join, and Alias, but then
also we have to repeat those three types in order to set up
_DMLTableElement.

Other change introduced here, there was a deannotate=True
for the left/right of a sql.join().    All tests pass without that.
I'd rather not have that there as if we have a join(A, B) where
A, B are mapped classes, we want them inside of the _annotations.
The rationale seems to be performance, but this performance can
be illustrated to be on the compile side which we hope is cached
in the normal case.

CTEs now accommodate for text selects including recursive.

Get typing to accommodate "util.preloaded" cleanly; add "preloaded"
as a real module.  This seemed like we would have needed
pep562 `__getattr__()` but we don't, just set names in
globals() as we import them.

References: #6810
Change-Id: I34d17f617de2fe2c086fc556bd55748dc782faf0

Fixes: #7795
Change-Id: Ib790581555656c088f86c00080c70d19ca295a03

__future__.annotations mode allows us to use non-string
annotations for argument and return types in most cases,
but more importantly it removes a large amount of runtime
overhead that would be spent in evaluating the annotations.

Change-Id: I2f5b6126fe0019713fc50001be3627b664019ede
References: #6810

includes new fix for formatting like black does.

also runs black on a few outliers.

Change-Id: I67446660a6bc10b73eb710389ae6d3f122af9302

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: Ia3357959ed286dc7d2ce264b5ddcadf309351ff7