database/sql: use reflect.TypeFor for known types

database/sql: use reflect.TypeFor for known types

For #60088

Change-Id: Ib05ba3d456b22f7370459037b3d263c4b3ebe3b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/514975
Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>