Add Quick Settings tile (#660)

* Add Quick Settings tile

- Add multi-client support to AmneziaVpnService
- Make AmneziaActivity permanently connected to AmneziaVpnService while it is running
- Refactor processing of connection state changes on qt side
- Add VpnState DataStore
- Add check if AmneziaVpnService is running

* Add tile reset when the server is removed from the application

client/android/src/org/amnezia/vpn/AmneziaApplication.kt

@@ -18,6 +18,7 @@ class AmneziaApplication : QtApplication(), CameraXConfig.Provider {
         super.onCreate()
         Prefs.init(this)
         Log.init(this)
+        VpnStateStore.init(this)
         Log.d(TAG, "Create Amnezia application")
         createNotificationChannel()
     }