Use global lock instead of NewExclusivePool to allow distributed lock between multiple Gitea instances (#31813)

Replace #26486 
Fix #19620

---------

Co-authored-by: Jason Song <i@wolfogre.com>

modules/setting/global_lock_test.go

@@ -0,0 +1,35 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLoadGlobalLockConfig(t *testing.T) {
+	t.Run("DefaultGlobalLockConfig", func(t *testing.T) {
+		iniStr := ``
+		cfg, err := NewConfigProviderFromData(iniStr)
+		assert.NoError(t, err)
+
+		loadGlobalLockFrom(cfg)
+		assert.EqualValues(t, "memory", GlobalLock.ServiceType)
+	})
+
+	t.Run("RedisGlobalLockConfig", func(t *testing.T) {
+		iniStr := `
+[global_lock]
+SERVICE_TYPE = redis
+SERVICE_CONN_STR = addrs=127.0.0.1:6379 db=0
+`
+		cfg, err := NewConfigProviderFromData(iniStr)
+		assert.NoError(t, err)
+
+		loadGlobalLockFrom(cfg)
+		assert.EqualValues(t, "redis", GlobalLock.ServiceType)
+		assert.EqualValues(t, "addrs=127.0.0.1:6379 db=0", GlobalLock.ServiceConnStr)
+	})
+}