TGeometryParticle::GeometrySharedLowLevel

Ryan: [FGeometryCollectionPhysicsProxy](API\Runtime\Chaos\PhysicsProxy\FGeometryCollectionPhysicsProxy) needs access to [GeometrySharedLowLevel()](API\Runtime\Chaos\Chaos\TGeometryParticle\GeometrySharedLowLevel), as it needs access for the same reason as ParticleData.