Ensure that schema search path is set with every connection on postgres (#14131)

Ensure that schema search path is set with every connection on postgres (#14131)

* Ensure that schema search path is set with every connection on postgres

Unfortunately every connection to postgres requires that the search path is
set appropriately.

This PR shadows the postgres driver to ensure that as soon as a connection
is open, the search_path is set appropriately.

Fix #14088

Signed-off-by: Andrew Thornton <art27@cantab.net>
* no golangci-lint that is not a helpful suggestion

Signed-off-by: Andrew Thornton <art27@cantab.net>
* Use Execer if available

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>