Request for adding preparedStatement name into logged query data

Hihi, I'm new to github so please bear with me and let me know if I should have done things differently...

Currently I'm running an app using pgx and I'm adding trace telemetry to honeycomb.

Yay: [conn.Exec](https://github.com/jackc/pgx/blob/master/conn.go#L424) seems to log out the preparedStatement name as sql.
Boo: query only logs the sqlQuery, but not the named preparedStatement (see below).

It would be fantastic to be able to see visually in honeycomb `PreparedStatementQueryName`. I know I can regex the SQL, but it just feels dirty.

```
myApp -> pgxpool.pool.Query
[pgxpool.pool.Query](https://github.com/jackc/pgx/blob/master/pgxpool/pool.go#L496)
[pgxpool.conn.Query](https://github.com/jackc/pgx/blob/master/pgxpool/conn.go#L54)
[conn.Query](https://github.com/jackc/pgx/blob/master/conn.go#L599)
[conn.getRows](https://github.com/jackc/pgx/blob/master/conn.go#L551) // Here we get the rows and set row.sql = sql, which is the preparedStatement DB func name.
[conn.Query](https://github.com/jackc/pgx/blob/master/conn.go#L646) // Here we set the rows.sql as sd.sql, which is the actual sqlQuery
[rows.Close](https://github.com/jackc/pgx/blob/master/rows.go#L146) // And finally we log, but only with data that includes the sqlQuery
```

It seems to me that rows.sql is only used for logging, but there would most likely always be a demand for having the query.

I would suggest:
1. adding name as a [row parameter](https://github.com/jackc/pgx/blob/master/rows.go#L105)
2. adding it to the [data that gets logged out](https://github.com/jackc/pgx/blob/master/rows.go#L146).

If this seems reasonable then I'm all for creating a PR myself with proposed changes.

Thanks a bunch - Húni

Start with rows.go around the row parameter and rows.Close logging, then trace conn.getRows and conn.Query as linked in the issue. Check how the prepared-statement name and SQL query are assigned. Done means logged query data includes the prepared-statement name without losing the SQL query.

Written by the indexing model from the issue text.