cherry-pick-applets/systemtray: fix xembed icon not receiving click events when using Qt scaling
On X11, when using Qt scaling, mapToGlobal will return a scaled position
which is unusable in SNIProxy::sendClick
. This fixes the bug by
multiplying the position by devicePixelRatio.
BUG: 456168 FIXED-IN: 5.27
(cherry picked from commit 8b1250ac)