Move remainings of Android Extras to qtbase as private APIs

Since not all APIs in extras have new cross-platform APIs under qtbase, we can move those remains to qtbase as private APIs for now until we have an alternative.

This is already done in https://codereview.qt-project.org/c/qt/qtbase/+/347462.

Those private apis can be used with core-private (qmake) or Qt::CorePrivate (cmake)

#include <QtCore/private/qandroidextras_p.h>