Support for disabling transactions

首先跟踪 issue 中所示的 create_pool 和 pool.acquire 用法，然后将其与 connection.transaction 的行为进行比较。在本地 CrateDB 实例上复现该工作负载，并确定隐式事务命令的发出位置。完成的标准是存在一种受支持的方式来禁用该行为，使所示的 insert 不会在 CrateDB 上失败。

• 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?: 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.