ToolBar: Fix eliding titles for specific fonts

QtQuick/TextMetrics can not be trusted. Meanwhile, QtQuick.Text provides
sane implicitWidth regardless of elided string (which in turn only
affects paintedWidth & contentWidth).

See also:
- https://bugreports.qt.io/browse/QTBUG-85936
- https://bugreports.qt.io/browse/QTBUG-83936
- https://bugreports.qt.io/browse/QTBUG-94023

BUG: 474881