conn.execute return value

还没有人认领这个 Issue。

asyncpg version: 0.30
PostgreSQL version:
Do you use a PostgreSQL SaaS? If so, which? Can you reproduce the issue with a local PostgreSQL install?:
Python version: 3.11
Platform: Ubuntu
Do you use pgbouncer?: No
Did you install asyncpg with pip?: Yes
If you built asyncpg locally, which version of Cython did you use?:
Can the issue be reproduced under both asyncio and [uvloop](https://github.com/magicstack/uvloop)?: NA

When I do `execute` on a connection, the return value looks like it brings back the number of rows with `SELECT ` prepended to it.

Example:
If you run:
```sql
conn.execute("SELECT now();")
```
The output is `SELECT 1`

If you run:
```sql
conn.execute("SELECT generate_series(0, 100);")
```
The output is `SELECT 101`

Obviously with a `fetch` it brings back the correct result, but I am specifically interested in the return value of a multi statement `execute`.

ie, I want to do
```sql
conn.execute("SELECT generate_series(0, 100); SELECT now();")
```
And the return value should be the last return value.

Is this possible? What am I missing?

Thanks in advance

And PS. The ISSUE_TEMPLATE is not applying when creating the issue, I copied it in.

从 conn.execute 入口开始，在报告的 asyncpg 0.30 和 Python 3.11 环境中复现单语句和多语句这两个示例。要视为完成，需要就 execute 的返回值达成行为共识或修改文档；该 issue 未指定文件或测试。

由索引模型根据 Issue 内容生成。