The new Mode menu introduced in D20958 is updated, removing the use of QListWidget.

This replaces:
QListWidget with QListView + QStandardItemModel
and KListWidgetSearchLine with QLineEdit

In addition, some changes are made:

• Decrease delay in displaying search results, after typing. The search clearing is done without delays.
• Add ToolTip in the search bar, with a brief description.

I also made small improvements to the code. From the user's point of view, this patch is almost imperceptible.