Support for disabling transactions

Personne n'a encore pris cette issue.

* **asyncpg version**: 0.28.0
* **PostgreSQL version**: CrateDB 5.4.2 https://github.com/crate/crate
* **Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
the issue with a local PostgreSQL install?**: Using CrateDB locally
* **Python version**: 3.11.4
* **Platform**: Linux arm64
* **Do you use pgbouncer?**: No
* **Did you install asyncpg with pip?**: Yes
* **If you built asyncpg locally, which version of Cython did you use?**: 0.29.36
* **Can the issue be reproduced under both asyncio and
[uvloop](https://github.com/magicstack/uvloop)?**: Yes

It would be really useful to be able to disable transaction support for Postgres-like database systems that don't support transactions.

CrateDB is an OLAP database with Postgres Wire Protocol support, however it does not have support for transactions. (`BEGIN` is a no-op, but `ROLLBACK` is an undefined term and causes issues)

Currently using asyncpg like this:

```
asyncpg_pool = await asyncpg.create_pool(**CRATE_DB_CONFIG, loop=loop, max_size=10)

async with asyncpg_pool.acquire() as connection:
await connection.execute("""insert into some_table (event_time, field1, field2) values ($1, $2, $3);""", datetime.now(), user_id, session_id)
```

I'm deliberately avoiding any `connection.transaction()` calls yet asyncpg still appears to wrap everything in a transaction block.

Commencez par retracer l’utilisation de create_pool et de pool.acquire présentée dans l’issue, puis comparez-la au comportement de connection.transaction. Reproduisez la charge de travail avec une instance locale de CrateDB et identifiez où les commandes de transaction implicites sont émises. Le travail est terminé lorsqu’il existe un moyen pris en charge de désactiver ce comportement afin que l’insert présenté n’échoue pas sur CrateDB.

Rédigé par le modèle d'indexation à partir du texte de l'issue.