cmd/compile: fix PGO cross-package inlining
cmd/compile: fix PGO cross-package inlining

With CL 447015, we identify hot callees from edge weights, but
the code only traverses edges for calls from the current package.
If the callee is in a different package, when compiling that
package, the edge was not visited, so the callee was not actually
marked inline candidate. This CL fixes it by traversing all hot
edges.

Change-Id: If668c1a16ebe34e3474376b88ab3a84be76b8562
Reviewed-on: https://go-review.googlesource.com/c/go/+/448015
Run-TryBot: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Michael Pratt <e7f1edc6d5aa9f6c8c377425db8f1a5816cbbb88@google.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go