runOnAndroidMainThread(): Use QThreadPool::start() instead of QtConcurrent::run()

The latter is in a module (QtConcurrent) that depends on QtCore. Don't
make QtCore depend on QtConcurrent...

The code doesn't use the QFuture returned from QtConcurrent::run(),
anyway, so QThreadPool::start(function<void()>) is more than an
adequate replacement.

Task-number: QTBUG-109586
Pick-to: 6.5 6.4 6.2
Change-Id: Id00a42525c3d7454a1fa2d4812de634dbbea1035
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

src/corelib/platform/android/qandroidnativeinterface.cpp

@@ -7,8 +7,10 @@
 #include <QtCore/private/qjnihelpers_p.h>
 #include <QtCore/qjniobject.h>
 #if QT_CONFIG(future) && !defined(QT_NO_QOBJECT)
-#include <QtConcurrent/QtConcurrent>
+#include <QtCore/qfuture.h>
+#include <QtCore/qfuturewatcher.h>
 #include <QtCore/qpromise.h>
+#include <QtCore/qthreadpool.h>
 #include <deque>
 #endif
 
@@ -160,7 +162,7 @@ QFuture<QVariant> QNativeInterface::QAndroidApplication::runOnAndroidMainThread(
     promise->start();
 
     if (!timeout.isForever()) {
-        (void) QtConcurrent::run([=, &future]() {
+        QThreadPool::globalInstance()->start([=, &future]() {
             QEventLoop loop;
             QTimer::singleShot(timeout.remainingTime(), &loop, [&]() {
                 future.cancel();