Fix QtQuickView multi-view examples

What?
QtQuickView multi-view examples experienced large changes due to https://codereview.qt-project.org/c/qt/qtdeclarative/+/606740. In that change some properties and files got overlooked and as such the examples no longer operate as intented. These features are mostly about scaling the eaxmple.

How to fix?
Check all the affected examples and files and bring back discarded scaling features, while simultaneously keeping the added changes meaningful to QTBUG-129288.