Fix some solver issues

- Fix the wrong codepath taken  by the solver for contacts involving a collider without parent.
- Properly adress the non-linear treatment of the friction direction
- Simplify the sleeping strategy
- Add an impulse resolution multiplier

src/pipeline/physics_pipeline.rs

@@ -179,6 +179,7 @@ impl PhysicsPipeline {
     {
         self.counters.stages.island_construction_time.resume();
         islands.update_active_set_with_contacts(
+            integration_parameters.dt,
             bodies,
             colliders,
             narrow_phase,