Add Graceful shutdown for Windows and hooks for shutdown of goroutines (#8964)

* Graceful Shutdown for windows and others

Restructures modules/graceful, adding shutdown for windows, removing and
replacing the old minwinsvc code.

Creates a new waitGroup - terminate which allows for goroutines to
finish up after the shutdown of the servers.

Shutdown and terminate hooks are added for goroutines.

* Remove unused functions - these can be added in a different PR

* Add startup timeout functionality

* Document STARTUP_TIMEOUT

modules/graceful/net_windows.go

@@ -0,0 +1,19 @@
+// +build windows
+
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+// This code is heavily inspired by the archived gofacebook/gracenet/net.go handler
+
+package graceful
+
+import "net"
+
+// GetListener obtains a listener for the local network address.
+// On windows this is basically just a shim around net.Listen.
+func GetListener(network, address string) (net.Listener, error) {
+	// Add a deferral to say that we've tried to grab a listener
+	defer Manager.InformCleanup()
+
+	return net.Listen(network, address)
+}