I faced an issue related to pg bouncer and prepared statement cache flow in asyncpg dialect. Regarding this discussion https://github.com/sqlalchemy/sqlalchemy/issues/6467 I prepared PR to support an optional parameter `name` in prepared statement which is allowed, since 0.25.0 version in `asyncpg` https://github.com/MagicStack/asyncpg/pull/846

**UPD:**
the issue with proposal: https://github.com/sqlalchemy/sqlalchemy/issues/9608

### Description
Added optional parameter `name_func` to `AsyncAdapt_asyncpg_connection` class which will call on the `self._connection.prepare()` function and populate a unique name.

so in general instead this

```python

from uuid import uuid4

from asyncpg import Connection

class CConnection(Connection):
    def _get_unique_id(self, prefix: str) -> str:
        return f'__asyncpg_{prefix}_{uuid4()}__'

engine = create_async_engine(...,
    connect_args={
        'connection_class': CConnection,
    },
)

```

would be enough

```python
from uuid import uuid4

engine = create_async_engine(...,
    connect_args={
        'name_func': lambda:  f'__asyncpg_{uuid4()}__',
    },
)

```

### Checklist
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This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [x] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Fixes: #9608
Closes: #9607
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/9607
Pull-request-sha: b4bc8d3e57ab095a26112830ad4bea36083454e3

Change-Id: Icd753366cba166b8a60d1c8566377ec8335cd828

<!-- Provide a general summary of your proposed changes in the Title field above -->

### Description
Fixes: #9509
<!-- Describe your changes in detail -->

### Checklist
<!-- go over following points. check them with an `x` if they do apply, (they turn into clickable checkboxes once the PR is submitted, so no need to do everything at once)

-->

This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [x] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Closes: #9510
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/9510
Pull-request-sha: 596648e7989327eef1807057519b2295b48f1adf

Change-Id: I7b527edda09eb78dee6948edd4d49b00ea437011

Restored the :paramref:`_postgresql.ENUM.name` parameter as optional in the
signature for :class:`_postgresql.ENUM`, as this is chosen automatically
from a given pep-435 ``Enum`` type.

Fixed issue where the comparison for :class:`_postgresql.ENUM` against a
plain string would cast that right-hand side type as VARCHAR, which due to
more explicit casting added to dialects such as asyncpg would produce a
PostgreSQL type mismatch error.

Fixes: #9611
Fixes: #9621
Change-Id: If095544cd1a52016ad2e7cfa2d70c919a94e79c1

Fixed critical regression in PostgreSQL dialects such as asyncpg which rely
upon explicit casts in SQL in order for datatypes to be passed to the
driver correctly, where a :class:`.String` datatype would be cast along
with the exact column length being compared, leading to implicit truncation
when comparing a ``VARCHAR`` of a smaller length to a string of greater
length regardless of operator in use (e.g. LIKE, MATCH, etc.). The
PostgreSQL dialect now omits the length from ``VARCHAR`` when rendering
these casts.

Fixes: #9511
Change-Id: If094146d8cfd989a0b780872f38e86fd41ebfec2

Added new PostgreSQL type :class:`_postgresql.CITEXT`. Pull request
courtesy Julian David Rath.

Fixes: #9416
Closes: #9417
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/9417
Pull-request-sha: 23a83a342ad6d820ee5749ebccda04e54c373f7d

Change-Id: I54699b9457426c20afbdc0acaa41dc57644b0536

these tests failed the day before DST here, so just use utc

Fixes: #9471
Change-Id: I3f5c940b4e7d36943bd3ad34cc06b9563371d171

Fixes: #9401
Change-Id: Ie10192348749567110f53ae618fc724f37d1a6a1

This adds the very small plugin flake8-import-single which
will prevent us from having an import with more than one symbol
on a line.

Flake8 by itself prevents this pattern with E401:

import collections, os, sys

However does not do anything with this:

from sqlalchemy import Column, text

Both statements have the same issues generating merge artifacts
as well as presenting a manual decision to be made.   While
zimports generally cleans up such imports at the top level, we
don't enforce zimports / pre-commit use.

the plugin finds the same issue for imports that are inside of
test methods.   We shouldn't usually have imports in test methods
so most of them here are moved to be top level.

The version is pinned at 0.1.5; the project seems to have no
activity since 2019, however there are three 0.1.6dev releases
on pypi which stopped in September 2019, they seem to be
experiments with packaging.  The source for 0.1.5
is extremely simple and only reveals one method to flake8
(the run() method).

Change-Id: Icea894e43bad9c0b5d4feb5f49c6c666d6ea6aa1