Timestep Smaller than 1.0 not Working

[DavidMansolino]

Describe the Bug
If the WorldInfo.timestep is smaller than 1.0 the simulation is not working as expected.

If the simulation doesn't have any controller:

• The real-time is not respected (even if in fast mode speed is >> 1.0x). This is probably related to the use of integer here:

  webots/src/webots/engine/WbSimulationWorld.hpp

  Line 78 in 0ebffff

  QList<int> mElapsedTimeHistory;

If the simulation has some controllers:

• The simulation get stuck, time doesn't increase. This seems related to the fact that isRequestPending is always returning false here:

  webots/src/webots/control/WbControlledWorld.cpp

  Line 364 in 6940794

  if (!controller->isRequestPending() || controller->isIncompleteRequest()) {