go/types, types2: enable new type inference

go/types, types2: enable new type inference

Enable new type inference and compare result with old inference
implementation - the result must be identical in a correct program.

Change-Id: Ic802d29fcee744f6f826d5e433a3d0c0e73b68e3
Reviewed-on: https://go-review.googlesource.com/c/go/+/464341
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>