Android: Make the device watcher process terminate on shutdown

Terminate on IPlugin::aboutToShutdown instead of
QCoreApplication::aboutToQuit. If needed synchronously.

Added "ADB device watcher started" logging.

Fixes: QTCREATORBUG-27118
Change-Id: I483659b018c74d179b64a5a4f17cc2c27c9598a8
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/android/androidplugin.cpp

@@ -160,6 +160,19 @@ bool AndroidPlugin::initialize(const QStringList &arguments, QString *errorMessa
     return true;
 }
 
+AndroidPlugin::ShutdownFlag AndroidPlugin::aboutToShutdown()
+{
+    AndroidDeviceManager *dm = AndroidDeviceManager::instance();
+    const IPlugin::ShutdownFlag sf = dm->devicesShutdownFlag();
+
+    if (sf == AsynchronousShutdown)
+        connect(dm, &AndroidDeviceManager::devicesWatcherShutdownFinished,
+                this, &ExtensionSystem::IPlugin::asynchronousShutdownFinished);
+
+    dm->shutdownDevicesWatcher();
+    return sf;
+}
+
 void AndroidPlugin::kitsRestored()
 {
     const bool qtForAndroidInstalled