Use the `bUseVRPreviewForPlayWorld` flag to determine if input sim should be enabled. This will use input sim in regular editor viewports, but also allow holographic remoting without having to disconnect the device.
Avoid restart requirement for toggling input simulation on and off. This requires that the engine subsystem is always created (only in editor). The IsInputSimulationEnabled or GetInputSimulationIfEnabled helper functions should be used to ensure the subsystem is only used when enabled.
(Submitted by Microsoft)
#jira UE-90411
#rb steve.smith
[CL 12354679 by steve smith in 4.25 branch]
