0026159: Visualization - revise tolerance implementation for selection

0026159: Visualization - revise tolerance implementation for selection

Max tolerance is now applied to all objects and entities by default;
if there is an entity with a lower tolerance, selecting frustum will be recalculated for it.
The ability to set sensitivity for each entity individually is moved to protected section of SelectBasics_SensitiveEntity
SetPixelTolerance from AIS_InteractiveContext now sets custom tolerance that is applied to all sensitives.
Added -unset option to vselprecision command to disable custom tolerances.
Test case for issue #26159