cmd/link: establish dependable package initialization order

As described here:

https://github.com/golang/go/issues/31636#issuecomment-493271830

"Find the lexically earliest package that is not initialized yet,
but has had all its dependencies initialized, initialize that package,
 and repeat."

Simplify the runtime a bit, by just computing the ordering required
in the linker and giving a list to the runtime.

Update #31636
Fixes #57411

RELNOTE=yes

Change-Id: I1e4d3878ebe6e8953527aedb730824971d722cac
Reviewed-on: https://go-review.googlesource.com/c/go/+/462035
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>

test/noinit.go

@@ -328,9 +328,8 @@ func init() {
 // Actual test: check for init funcs in runtime data structures.
 
 type initTask struct {
-	state uintptr
-	ndeps uintptr
-	nfns  uintptr
+	state uint32
+	nfns  uint32
 }
 
 //go:linkname main_inittask main..inittask