applets/systemtray: Include heading in back button

• applets/systemtray: Include heading in back button

Increases the hit area of the button significantly.

Reason for the change

Increases the hit area of the button significantly.

(imho we should also do this in Kirigami ;)

Test plan

• hidden items list still shows “Status & Notifications” with no arrow
• verified that the back arrow isn’t shown then
• verified that it still elides properly but that the button is only the size of the heading
• going back still works
• “always show all items” has the back button disabled as before
• also appears to work well with plasmashell -reverse

Not sure how that will impact a screen reader, though.

Screenshots or screen recordings

Should look virtually identical except that you can now click the entire heading text to go back

Bugs fixed

Pretty sure I saw a bug about this a while ago but couldn’t find it