go/types,types2: superficial changes to align types and types2

This CL contains an assortment of superficial fixes noticed while
self-reviewing the most recent stack of ports. It also makes a couple
adjustments to termlist_test.go, in both go/types and
cmd/compile/internal/types2.

Change-Id: I64c8cda5e1704e86ac11c6ffc86d55248f44ef79
Reviewed-on: https://go-review.googlesource.com/c/go/+/342490


Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>