[release-branch.go1.17] go/types: break cycles in invalid types

This is a partial port of CL 354329 from types2 to go/types.
It contains an adjustment to type.go to deal with possibly
invalid type bounds.

Fixes #48825.
For #48819.

Change-Id: I9efdcdbfa6432f3cee64d924a4c67ecc6793cf86
Reviewed-on: https://go-review.googlesource.com/c/go/+/354349


Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/368456
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>