Cannot use datetimes before UNIX epoch on Windows

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* **asyncpg version**: 0.29.0
* **PostgreSQL version**: 15.5
* **Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
the issue with a local PostgreSQL install?**: Local PostgreSQL install
* **Python version**: 3.10.1
* **Platform**: Windows
* **Do you use pgbouncer?**: No
* **Did you install asyncpg with pip?**: Yes
* **If you built asyncpg locally, which version of Cython did you use?**: N/A
* **Can the issue be reproduced under both asyncio and
[uvloop](https://github.com/magicstack/uvloop)?**: N/A

If I have this query:

```sql
INSERT INTO process.start_and_end (user_id, process_id, start_dt, end_dt) VALUES ($1, $2, $3, $4);
```

and in Python I do:

```python
await conn.executemany(query, [(1325, 1001, datetime.datetime(1969, 12, 31, 0, 0), None)])
```

this line throws the following exception:

```
Traceback (most recent call last):
File "asyncpg\protocol\prepared_stmt.pyx", line 175, in asyncpg.protocol.protocol.PreparedStatementState._encode_bind_msg
File "asyncpg\protocol\codecs/base.pyx", line 227, in asyncpg.protocol.protocol.Codec.encode
File "asyncpg\protocol\codecs/base.pyx", line 129, in asyncpg.protocol.protocol.Codec.encode_scalar
File "asyncpg\pgproto\./codecs/datetime.pyx", line 222, in asyncpg.pgproto.pgproto.timestamptz_encode
OSError: [Errno 22] Invalid argument

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "main.py", line 919, in
loop.run_until_complete(async_main())
File "C:\Scoop\apps\python\current\lib\asyncio\base_events.py", line 641, in run_until_complete
return future.result()
[...]
File "main.py", line 401, in __insert_tape
await conn.executemany(query, [(1325, 1001, datetime.datetime(1969, 12, 31, 0, 0), None)])
File ".venv\lib\site-packages\asyncpg\connection.py", line 391, in executemany
return await self._executemany(command, args, timeout)
File ".venv\lib\site-packages\asyncpg\connection.py", line 1911, in _executemany
result, _ = await self._do_execute(query, executor, timeout)
File ".venv\lib\site-packages\asyncpg\connection.py", line 1945, in _do_execute
result = await executor(stmt, None)
File "asyncpg\protocol\protocol.pyx", line 267, in bind_execute_many
File "asyncpg\protocol\coreproto.pyx", line 974, in asyncpg.protocol.protocol.CoreProtocol._bind_execute_many_more
File "asyncpg\protocol\protocol.pyx", line 230, in genexpr
File "asyncpg\protocol\prepared_stmt.pyx", line 204, in asyncpg.protocol.protocol.PreparedStatementState._encode_bind_msg
asyncpg.exceptions.DataError: invalid input for query argument $3 in element #0 of executemany() sequence: datetime.datetime(1969, 12, 31, 0, 0) ([Errno 22] Invalid argument)
```

Digging into it a bit more, I found that the culprit is [this line in the codec for datetime objects](https://github.com/MagicStack/py-pgproto/blob/master/codecs/datetime.pyx#L222), which is related to this old CPython issue on Windows: https://github.com/python/cpython/issues/80940.

The fix looks quite simple, but unfortunately I do not have the time to work on that, so I'm opening an issue instead of a PR.

Start with the linked line in py-pgproto's codecs/datetime.pyx and compare its behavior with the referenced CPython Windows issue. Reproduce the datetime.datetime(1969, 12, 31) bind through executemany() on Windows. Done means pre-UNIX-epoch datetimes no longer raise OSError during encoding.

Written by the indexing model from the issue text.