cmd/compile: use types2.Sizes instead of compiler own implementation

cmd/compile: use types2.Sizes instead of compiler own implementation

With #61035 fixed, types2.Sizes matches the compiler behavior, so use its
Sizes implementation instead of rolling our own copy.

Updates #61035

Change-Id: I7b9efd27a01f729a04c79cd6b4ee5f417fe6e664
Reviewed-on: https://go-review.googlesource.com/c/go/+/506716
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>