Update KDE Frameworks to latest upstream release, 5.61

Release notes at
https://kde.org/announcements/kde-frameworks-5.61.0.php

Thanks to
antoine@ for the exp-runs,
tcberner@ for most of the prep-work,
the Gentoo community for cherry-picking patches

There are a bunch of changes in (implicitly included) headers, which
broke existing KDE Applications builds; that's why there are a whole
bunch of "patch-gentoo-kf5-5.61-headers" patches (taken from Gentoo
packaging). Those will go away with the next KDE Applications release,

PR: 239777
Submitted by: tcberner