Improve quick settings tiles reliability

Android apparently can decide to kill TileService when there are too many. Therefore, let's check if our service is connected before doing anything.

Source: https://android.googlesource.com/platform/frameworks/base/+/e1d13c9/packages/SystemUI/src/com/android/systemui/qs/external/TileServices.java#52

mobile/src/main/java/be/mygod/vpnhotspot/util/KillableTileService.kt

@@ -0,0 +1,19 @@
+package be.mygod.vpnhotspot.util
+
+import android.content.ComponentName
+import android.content.ServiceConnection
+import android.os.IBinder
+import android.service.quicksettings.TileService
+import androidx.annotation.RequiresApi
+
+@RequiresApi(24)
+abstract class KillableTileService : TileService(), ServiceConnection {
+    protected var tapPending = false
+
+    override fun onServiceConnected(name: ComponentName?, service: IBinder?) {
+        if (tapPending) {
+            tapPending = false
+            onClick()
+        }
+    }
+}