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: https://github.com/cyberbotics/webots/blob/0ebffffa962912c5a4ba715244ce10c8f8c598d1/src/webots/engine/WbSimulationWorld.hpp#L78

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: https://github.com/cyberbotics/webots/blob/69407941af3e3347fefcbf7cd74ebea13fdc917e/src/webots/control/WbControlledWorld.cpp#L364