[dev.regabi] cmd/compile: change NodeSet to NameSet
The only user of NodeSet (computing initialization dependencies) only
needs to store *Names in this structure. So change its definition to
match that need, and update the code in initorder.go accordingly.
Passes buildall w/ toolstash -cmp.
Updates #42982.
Change-Id: I181a8aaf9bc71e88f4ac009c4f381a718080e48f
Reviewed-on: https://go-review.googlesource.com/c/go/+/275752
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>