kickoff: various small improvements
I realize grabbag MRs are usually not a good idea, but these are all so small that it wouldn't be worth the reviewer's or patch author's time to separate them.
- kickoff: remove extendHoverMargins property
- we can just check if view is ListView instead.
- kickoff: set scrolling speed to be like PC3 ScrollView
- kickoff: make section label width use KickoffListView::availableWidth
- This is slightly better code since it's based on the real available width instead of the contentItem width.
- KickoffItemDelegate: remove mouseArea property
- we don't need it
- KickoffItemDelegate: add comment explaining why there's an Item for dragging
- KickoffItemDelegate: open menu in onPressed
- We normally try to open right click menus on press like Qt Widgets.
- KickoffItemDelegate: move selection and focus to onPressed
- Select and focus on press to improve responsiveness and touch feedback.
- KickoffItemDelegate: Only use onPressAndHold with left click
- Doing it with all buttons isn't needed and is unexpected.