Transaction leak in transform_stream

[levkk]

I'm seeing this in Postgres logs when using transform_stream:

WARNING:  there is no transaction in progress

which tells me there is a synchronization issue between the SQLx client and the server. It attempts to solve that by issuing a rollback and that's the warning that pops up. I'm guessing this has something to do with the Stream implementation for the Transaction, but I haven't been able to trace it. The transaction is probably getting dropped (or leaked).

Imo if we can we should simplify that implementation a bit, maybe by defining less standard-compliant iterators and more custom ones that we manually iterate on using while let Some(v) = stream_iterator.next().await.