qt6, test: Use qWarning() instead of QWARN() macro
The QWARN() macro internally uses QTest::qWarn(), which has been
deprecated since Qt 6.3. Replacing it with qWarning() ensures
compatibility across all Qt versions.
qt6, test: Handle deprecated QVERIFY_EXCEPTION_THROWN
This change ensures compatibility across all supported Qt versions.
Co-Authored-By: João Barbosa <joao.paulo.barbosa@gmail.com>
This is a backport of core-gui#839
Depends on D18199