Fix result expression for grouped statements

[dellisd]

Fixes #4374

[hfhbd]

@dellisd I was curios why your fix didn't work so I tried it locally and fixed it. Are you okay with the commit?
Reason in async we generate this code:

override fun <R> execute(...): QueryResult<R> = QueryResult.AsyncValue {
  transactionWithResult {
    driver.execute(...).await()
    driver.executeQuery(...).await()
  }
}

To compare, in sync we return transactionWithResult directly:

override fun <R> execute(...): QueryResult<R> = transactionWithResult {
  driver.execute(...)
  driver.executeQuery(...)
}

Maybe we should use some suspend transaction directly?

[hfhbd]

We should add an async test too.

[dellisd]

Thanks @hfhbd!