Verify and document capability to ROS 2 simulation non-realtime.

[michalpelka]

Is your feature request related to a problem? Please describe.
A lot of other simulation products support non-realtime simulation.
That is useful in scenarios like:

• complex, challenging mechanical systems (e.g. humanoid robots),
• hardware in the loop simulation,
• potentially using non-realtime, non-game physics engines in O3DE for simulation
• using prerecorded data (e.g. from real system, or other simulation software)

Describe the solution you'd like
Detailed documentation both in gem source code and in o3de.org on:

• Current support for non-realtime simulation,
• Current support for external time source (provided by /clock to the o3de simulation from the other engine (e.g. Gazebo) or ROS 2 bag file.
• Explain known technological limitations (PhysX, Atom integration, ROS 2 cameras, RGL lasers)
• Test the whole ROS 2 Gem functionality (both by running simulation and code review) to find bugs like In many places in the code, deltaTime, that is not a real deltaTime is used to compute speeds, feedback, and other #709.
• Document Modified clock design, added new time source #707.

A good start is to set PhysX to work slower than real-time:

As you can see in the video, the clock respects correctly the slower time, when StableClock is used:
https://github.com/o3de/o3de-extras/assets/3209244/4ee3f59f-314e-4ef5-8838-c41152b0a9e0

Describe alternatives you've considered

Additional context
No more context.

[michalpelka]

Please review PR in process : https://github.com/o3de/o3de-extras/pull/714/files

[michalpelka]

Here is a branch that allows you to change physics speed https://github.com/RobotecAI/o3de/tree/mp/physx_realtime_factor