Added registry setting to SteadyClock that allows to disable resettin…

[michalpelka]

…g the clock when level is reloaded.

This is useful when you want to keep the clock running between level reloads, for example to keep some ROS 2 nodes happy that are running in the background, and you are reload / reset the level.

What does this PR do?

It is new feature.
It is optional, it does not change default behavior.

How was this PR tested?

Tested in external project against 2409.1
with registry adjusted:

{
    "O3DE":
    {
        "InputSystem":
        {
            "Mouse":
            {
                "CaptureMouseCursor": false
            }
        },
        "ROS2":
        {
            "SteadyClock" : true,
            "SteadyClock":
            {
                "ResetTimestampOnLevelReload": false
            },
            "Camera":
            {
                "AllowPipelineModification": false
            }
        }
    }
}

[jhanca-robotecai]

The code works as expected (changing via registry works); the default setting does not change the expected behavior. The feature makes sense - approve.

I rebased the code, clang-formatted, and force-pushed to ensure AR would have less issues.