AsyncTask: Centralize setting global future synchronizer

Move the global FutureSynchronizer to Utils and use it
by default for AsyncTask (if that is in the main thread).
This way setting a synchronizer is less prone to be forgotten.
Individual uses can still override this.

Change-Id: I1a12bf4d7f4cb5be99668bf0a4797108c2fe6448
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/android/androidsdkdownloader.cpp

@@ -8,14 +8,11 @@
 
 #include <coreplugin/icore.h>
 
-#include <extensionsystem/pluginmanager.h>
-
 #include <solutions/tasking/barrier.h>
 #include <solutions/tasking/networkquery.h>
 
 #include <utils/async.h>
 #include <utils/filepath.h>
-#include <utils/futuresynchronizer.h>
 #include <utils/networkaccessmanager.h>
 #include <utils/unarchiver.h>
 
@@ -170,7 +167,6 @@ GroupItem downloadSdkRecipe()
             return SetupResult::StopWithError;
         async.setConcurrentCallData(validateFileIntegrity, *storage->sdkFileName,
                                     androidConfig().getSdkToolsSha256());
-        async.setFutureSynchronizer(ExtensionSystem::PluginManager::futureSynchronizer());
         storage->progressDialog->setRange(0, 0);
         storage->progressDialog->setLabelText(Tr::tr("Verifying package integrity..."));
         return SetupResult::Continue;