TUN-6696: Refactor flow into funnel and close idle funnels

A funnel is an abstraction for 1 source to many destinations.
As part of this refactoring, shared logic between Darwin and Linux are moved into icmp_posix

ingress/icmp_windows_test.go

@@ -9,6 +9,7 @@ import (
 	"io"
 	"net/netip"
 	"testing"
+	"time"
 	"unsafe"
 
 	"golang.org/x/net/icmp"
@@ -72,7 +73,7 @@ func TestParseEchoReply(t *testing.T) {
 
 //  TestSendEchoErrors makes sure icmpSendEcho handles error cases
 func TestSendEchoErrors(t *testing.T) {
-	proxy, err := newICMPProxy(localhostIP, &noopLogger)
+	proxy, err := newICMPProxy(localhostIP, &noopLogger, time.Second)
 	require.NoError(t, err)
 	winProxy := proxy.(*icmpProxy)