[dev.regabi] cmd/compile: clean up Name and Func uses

[dev.regabi] cmd/compile: clean up Name and Func uses

Now that we have specific types for ONAME and ODCLFUNC nodes
(*Name and *Func), use them throughout the compiler to be more
precise about what data is being operated on.

This is a somewhat large CL, but once you start applying the types
in a few places, you end up needing to apply them to many other
places to keep everything type-checking. A lot of code also melts
away as types are added.

Passes buildall w/ toolstash -cmp.

Change-Id: I21dd9b945d701c470332bac5394fca744a5b232d
Reviewed-on: https://go-review.googlesource.com/c/go/+/274097
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>