aggregate text for KRunner in DesktopView
Aggregate text for KRunner in DesktopView to prevent eating fast-typed characters.
CCBUG: 416145
partial solution: resolved for DesktopView, not resolved for running KRunner from shortcut
Test Plan:
When DesktopView is focused, typed characters show KRunner query.
All fast-typed characters should now appear correctly in KRunner window,
instead of only first typed character.