[release-branch.go1.18] go/types, types2: disable inference for type instances

Inference for type instances has dependencies on type-checking order
that can lead to subtle bugs. As explained in #51527, disable it for
1.18.

Fixes #51527

Change-Id: I42795bad30ce53abecfc5a4914599ae5a2041a9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/387934


Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 28fab5ef)
Reviewed-on: https://go-review.googlesource.com/c/go/+/390576


Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>