go/types, types2: ensure invalid generic types are marked as invalid

go/types, types2: ensure invalid generic types are marked as invalid

When detecting invalid types, we may detect cycles through instances.
Ensure that the uninstantiated origin type is also marked invalid.

Fixes #56665

Change-Id: Id67653bcb072ac80161dea07d0ced566e61564a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/449275
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>