Interface to avoid Prepare in CopyFrom

[cevian]

Is your feature request related to a problem? Please describe.
Right now CopyFrom requires a Prepare and as far as I could tell this is just used to get type information.

Describe the solution you'd like
I think the default CopyFrom interface should stay as-is but I would like an alternative "Power User" API that allows me to avoid the Prepare on every call to CopyFrom. Using a cache would work as well.

I am happy to submit a PR if I can get some guidance on how you would like me to implement this.

[cevian]

Oh I missed that this is a duplicate of #1085, closing.

[alejandrodnm]

This will be solved in #1412 by passing either QueryExecModeExec or QueryExecModeSimpleProtocol as the last argument of CopyFrom. Instead of doing the prepare statement it will use the type map between golang and postgresql data types.