go/types, types2: add Sizes computation to match gc behavior

go/types, types2: add Sizes computation to match gc behavior

Fixes #60431
Fixes #60734
Fixes #61035

Change-Id: I82513da3e1714e8271fae220fe242bf2bfb4eb9d
Reviewed-on: https://go-review.googlesource.com/c/go/+/506856
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>