pgx v5 support

[elee1766]

any plans to upgrade or make another postgres wrapper which supports pgx v5?

pgxv5 performance is a good amount better, because it has a lot more reuse of connection read buffers. this is actually something we ran into with upper using both the SQL and pgxv4 driver. we ended up resolving the problem through just rewriting the resource hungry query routines in pgxv5 in a separate connection. currently we are avoiding the use of upper/db in our app unless necessary because of this.

I actually did this upgrade a while ago, ran into and fixed some problems with timezones, but otherwise the tests passed and it worked with my app. this is before v5 was released as stable.

would be happy to give another go at pgxv5 adapter for upper now that pgx v5 isn't in alpha and PR if this is something you guys would accept.

upper is still the best solution we've found for batching the upload of different structs via their tags.