qgs3dmapscene: Ensure to update near/far planes on new entity creation

The near/far planes are computed in `Qgs3DMapScene` when the camera
parameters have changed. Their values depend on the bounding boxes of
the visible entities. However, the near and far planes are not
recomputed when a new entity is added.
This can be problematic for entities from a vector layer because their
vertical extent is unknown when the associated bounding boxes are
created.

This issue is fixed by calling
`Qgs3DMapscene::updateCameraNearFarPlanes` when a new scene entity is
created. Indeed, on a new scene entity, the exact exact bounding box
has been computed by the loader of the chunked entity.

src/3d/qgs3dmapscene.cpp

@@ -698,6 +698,8 @@ void Qgs3DMapScene::addLayerEntity( QgsMapLayer *layer )
         connect( sceneNewEntity, &Qgs3DMapSceneEntity::newEntityCreated, this, [this]( Qt3DCore::QEntity * entity )
         {
           finalizeNewEntity( entity );
+          // this ensures to update the near/far planes with the exact bounding box of the new entity.
+          updateCameraNearFarPlanes();
         } );
 
         connect( sceneNewEntity, &Qgs3DMapSceneEntity::pendingJobsCountChanged, this, &Qgs3DMapScene::totalPendingJobsCountChanged );