Replace obsolete KIO::stat

In version 5.69 of KIO,

KIO::stat(const QUrl&, KIO::StatJob::StatSide, short int, JobFlags)

is deprecated in favor of

KIO::statDetails(const QUrl, KIO::StatJob::StatSide, KIO::StatDetails, JobFlags)

Test needed :

• compile on distro having KIO < 5.69
• compile on distro having KIO >= 5.69
• the component involved is Splitter, both the split action and the combine action