The user defined query geometry handling has been broken in several ways.
The previous way of defining a query geometry was using the non const
`getQueryGeometry` method and overriding its members. But then
`OcclusionQueryNode` wasn't aware of the geometry change and couldn't
internally handle it correctly.
The `computeBound` method never considered a user defined query geometry and
always just overrode the vertices of the geometry.
The member `_validQueryGeometry` wasn't correctly set.
This change should fix all this issues by introducing a small backward
compatibility break. The non const `getQueryGeometry` method is removed
forcing the user to use the `setQueryGeometry` method. But then `OcclusionQueryNode`
is aware of the user defined query geometry and can handle it correctly.
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