go/types: use internal/types/errors instead of local error codes

go/types: use internal/types/errors instead of local error codes

This change adds a new dependency to go/types.

Change-Id: I7e40b95c8c1e1356b638fc1aa2ef16ce91e9a496
Reviewed-on: https://go-review.googlesource.com/c/go/+/439563
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>