[dev.link] cmd/link: remove patchDWARFName from the linker

[dev.link] cmd/link: remove patchDWARFName from the linker

Remove the various bits of code in the linker that patch DWARF name
attributes (rewrite "". to packagepath).

Change-Id: I29a38d680d411ccf1c1eeb760f2d15fc8ec22d90
Reviewed-on: https://go-review.googlesource.com/c/go/+/222719
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>