Fix a crash that happens when resizing quick tiled window

QuickTile::setRelativeGeometry() and QuickRootTile::setVerticalSplit() or
QuickRootTile::setHorizontalSplit() can hit recursion when size
constraints start taking effect.

This change reworks how other quick tiles are resized. With the proposed
design, when relative geometry changes, QuickRootTile will notice that
and start resizing other tiles.

When QuickRootTile resizes horizontal or vertical split, it is going to
ignore QuickRootTile::relativeGeometryChanged() signals (m_resizedTile).
It prevents hitting the recursion and makes moving h/v splits more
predictable.

I do think that in order to make the tile design more robust to this
kind of bugs, it's worth splitting geometry in two kinds though - the
one that indicates the preferred geometry (implicitWidth/implicitHeight
in qtquick lingua) and the current geometry, the parent node then
monitors the preferred geometries and updates the current geometries.

BUG: 464621


(cherry picked from commit 826fb1cb)