Least load balancer (#2999)

* v5: Health Check & LeastLoad Strategy (rebased from 2c5a71490368500a982018a74a6d519c7e121816)

Some changes will be necessary to integrate it into V2Ray

* Update proto

* parse duration conf with time.Parse()

* moving health ping to observatory as a standalone component

* moving health ping to observatory as a standalone component: auto generated file

* add initialization for health ping

* incorporate changes in router implementation

* support principle target output

* add v4 json support for BurstObservatory & fix balancer reference

* update API command

* remove cancelled API

* return zero length value when observer is not found

* remove duplicated targeted dispatch

* adjust test with updated structure

* bug fix for observer

* fix strategy selector

* fix strategy least load

* Fix ticker usage

ticker.Close does not close ticker.C

* feat: Replace default Health Ping URL to HTTPS (#1991)

* fix selectLeastLoad() returns wrong number of nodes (#2083)

* Test: fix leastload strategy unit test

* fix(router): panic caused by concurrent map read and write (#2678)

* Clean up code

---------

Co-authored-by: Jebbs <qjebbs@gmail.com>
Co-authored-by: Shelikhoo <xiaokangwang@outlook.com>
Co-authored-by: 世界 <i@sekai.icu>
Co-authored-by: Bernd Eichelberger <46166740+4-FLOSS-Free-Libre-Open-Source-Software@users.noreply.github.com>
Co-authored-by: 秋のかえで <autmaple@protonmail.com>
Co-authored-by: Rinka <kujourinka@gmail.com>

app/router/weight_test.go

@@ -0,0 +1,60 @@
+package router_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/xtls/xray-core/app/router"
+)
+
+func TestWeight(t *testing.T) {
+	manager := router.NewWeightManager(
+		[]*router.StrategyWeight{
+			{
+				Match: "x5",
+				Value: 100,
+			},
+			{
+				Match: "x8",
+			},
+			{
+				Regexp: true,
+				Match:  `\bx0+(\.\d+)?\b`,
+				Value:  1,
+			},
+			{
+				Regexp: true,
+				Match:  `\bx\d+(\.\d+)?\b`,
+			},
+		},
+		1, func(v, w float64) float64 {
+			return v * w
+		},
+	)
+	tags := []string{
+		"node name, x5, and more",
+		"node name, x8",
+		"node name, x15",
+		"node name, x0100, and more",
+		"node name, x10.1",
+		"node name, x00.1, and more",
+	}
+	// test weight
+	expected := []float64{100, 8, 15, 100, 10.1, 1}
+	actual := make([]float64, 0)
+	for _, tag := range tags {
+		actual = append(actual, manager.Get(tag))
+	}
+	if !reflect.DeepEqual(expected, actual) {
+		t.Errorf("expected: %v, actual: %v", expected, actual)
+	}
+	// test scale
+	expected2 := []float64{1000, 80, 150, 1000, 101, 10}
+	actual2 := make([]float64, 0)
+	for _, tag := range tags {
+		actual2 = append(actual2, manager.Apply(tag, 10))
+	}
+	if !reflect.DeepEqual(expected2, actual2) {
+		t.Errorf("expected2: %v, actual2: %v", expected2, actual2)
+	}
+}