applets/systemtray: Use more international-friendly grid layout

Reason for the change

The current square grid layout in the hidden items view does not work well for languages with long strings and especially long words. Let's fix this by putting the icon next to the text and having only two columns, leaving more room for text.

This is a good compromise between the current layout and the old list view, which avoided the problem but was not very space-efficient or touch-friendly, and left a lot of ugly empty space on the right.

Test plan

Open the System Tray's expanded view after changing the language to something else, e.g.:

• LANGUAGE=de_DE plasmashell
• LANGUAGE=ru_RU plasmashell

Screenshots or screen recordings

Before	After

Bugs fixed

N/A

@teams/vdg @teams/usability @broulik