applets/systemtray: fix xembed icon not receiving click events when screen scale > 1 on Wayland

Fushan Wenrequested to merge
work/fuf/456168 into master

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

Scaled by app Scaled by system
Screenshot_20230123_205700 Screenshot_20230123_205855
Screenshot_20230123_205720 Screenshot_20230123_205923

Ref: plasma-desktop#34 (closed)

Edited by Fushan Wen

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