Routing: process supports UID on Android (#5915)

Example: https://github.com/XTLS/Xray-core/pull/5915#issuecomment-4232122895

---------

Co-authored-by: 风扇滑翔翼 <Fangliding.fshxy@outlook.com>

common/net/find_process_android.go

@@ -0,0 +1,20 @@
+//go:build android
+
+package net
+
+import (
+	"github.com/xtls/xray-core/common/errors"
+)
+
+var androidProcessFinder func(network, srcIP string, srcPort uint16, destIP string, destPort uint16) (int, string, string, error)
+
+func RegisterAndroidProcessFinder(f func(network, srcIP string, srcPort uint16, destIP string, destPort uint16) (int, string, string, error)) {
+	androidProcessFinder = f
+}
+
+func FindProcess(network, srcIP string, srcPort uint16, destIP string, destPort uint16) (int, string, string, error) {
+	if androidProcessFinder != nil {
+		return androidProcessFinder(network, srcIP, srcPort, destIP, destPort)
+	}
+	return 0, "", "", errors.New("android process lookup must be registered before use")
+}