go/types, types2: use "invalid recursive type" instead of "illegal cycle" in error...

go/types, types2: use "invalid recursive type" instead of "illegal cycle" in error messages

This matches long-standing compiler behavior.

For #55326.

Change-Id: Ic5aa0dfb08d035f2c33532cc463c73a55cc020a9
Reviewed-on: https://go-review.googlesource.com/c/go/+/433055
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>