TUN-6586: Change ICMP proxy to only build for Darwin and use echo ID to track flows

ingress/icmp_generic.go

@@ -0,0 +1,15 @@
+//go:build !darwin
+
+package ingress
+
+import (
+	"fmt"
+	"net"
+	"runtime"
+
+	"github.com/rs/zerolog"
+)
+
+func newICMPProxy(listenIP net.IP, logger *zerolog.Logger) (ICMPProxy, error) {
+	return nil, fmt.Errorf("ICMP proxy is not implemented on %s", runtime.GOOS)
+}