database/sql: prefer to return Rows.lasterr rather then a static error
database/sql: prefer to return Rows.lasterr rather then a static error

Fixes #25829

Change-Id: I400fdaf0ef3a23bc0d61c4873ffa298e0cf0fc6a
Reviewed-on: https://go-review.googlesource.com/c/145204
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

cloudflare/go,akutz/go,josharian/go,golang/go,cloudflare/go,cloudflare/go,akutz/go,cloudflare/go,akutz/go,CAFxX/go,akutz/go,josharian/go,nawawi/go,akutz/go,golang/go,CAFxX/go,CAFxX/go,CAFxX/go,golang/go,akutz/go,golang/go,golang/go,nawawi/go,akutz/go,josharian/go,cloudflare/go,cloudflare/go,josharian/go,josharian/go,josharian/go,CAFxX/go,CAFxX/go,akutz/go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,josharian/go,nawawi/go,nawawi/go,golang/go,golang/go,josharian/go,nawawi/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go