[dev.unified] cmd/compile: only sort symbols by name and package path

[dev.unified] cmd/compile: only sort symbols by name and package path

Since CL 393715, the path of package being compiled is now always known,
so symbols can be sorted by package path instead of package height.

Updates #51734

Change-Id: Ie543e2fdef4b93f3f0b97c6bcec0a4dcff788f2c
Reviewed-on: https://go-review.googlesource.com/c/go/+/410654
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>