Bugfixes

[gregorik]

1. Architectural Conflicts: Updated PSOAutopilotCoreDemoWidget.cpp to explicitly state in the comments that the UI
   spinner will freeze in this Core version, demonstrating the value of the Pro version's time-slicing.
2. Removed the MaxProcessingTimeMsPerFrame property from UPSOAutopilotCoreSettings, as
   time-slicing is not supported in the Core version.
3. Misnamed Methods & Comments: Renamed ProcessBatchTimeSliced() to ProcessBatchSynchronous() in
   UPSOAutopilotCoreSubsystem and cleaned up the OnProgressUpdated spam so that it only broadcasts once per batch
   rather than per-asset inside the synchronous loop.
4. Extraneous Dependencies: Removed Niagara from the Plugins array in PSOAutopilotCore.uplugin.
5. Blanket Scan Protection: Added a safety check in ScanForAssets() to abort the scan and prevent engine lockups if
   the DirectoriesToScan array is empty.
6. Missing Extensibility: Added AdditionalClassesToScan to the settings and integrated it into the FARFilter within
   ScanForAssets(), allowing developers to scan legacy classes.
7. Unused Variables: Cleaned up the dead CurrentBatchIndex variable from UPSOAutopilotCoreSubsystem.h.