Amends edd983071e.
Remove redundant calls to AAssetDir_getNextFileName() in
AndroidAbstractFileEngine::setFileName(). It's enough to check
if AAssetManager_open() returns null and AAssetManager_openDir() is
valid for the provided asset file name.
As part of this fix, add some unit tests to cover/ensure assets
listing/iterating works as expected.
Fixes: QTBUG-107627
Pick-to: 6.4 6.2 5.15
Change-Id: I37ae9cb64fbbc60699bb748895f77fd6a34fae1f
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>