cherry-pick-applets/systemtray: fix xembed icon not receiving click events when screen scale > 1 on Wayland
On Wayland, when using "Scaled by application", mapToGlobal will return a scaled position which is unusable in SNIProxy::sendClick. This fixes the bug by multiplying the position by devicePixelRatio.
BUG: 448050 CCBUG: 456168 FIXED-IN: 5.27
(cherry picked from commit 033b9dd1)