exec logging causes logQueryArgs to be created about pgx

[jackc]

For the Query and Exec paths there is minimal measurable time overhead, though there is a bit of extra memory allocations for the GC to handle.

Where it really causes problems is it is expensive enough to make it impractical to do much debug logging. I started to implement debug logging down at the individual PostgreSQL message level, but there the overhead was far too high event when the log was a nop.

I've thought about adding methods like InfoEnabled() bool to the interface, but it would have to be optional to avoid breaking compatibility with existing packages. And I'd be a bit worried about ruining performance for those loggers that don't have that type support.