Port SymbologyImpl Esri processors to the ArcGIS 300 QFuture async API

TaskWatcher (searchSymbols/fetchSymbol/createSwatch + completion signals) -> QFuture (searchSymbolsAsync/fetchSymbolAsync/createSwatchAsync + QFutureWatcher finished/result getter); flat arcgis/ includes; arcgisversion.h shim (external SDK). advancedSymbology now builds+links vs 300 (0 errors); SymbologyXML CTest 6/6, 0 assertion failures. Migration-only vs legacy; one documented forced delta: 300 has no spec-only DictionarySymbolStyle. Summary: MIGRATION_SUMMARY_ARCGIS300_SYMBOLOGY.md.

qt6-after/qt6-migrated-legatus/Lts/Viewer/SituationMap/Map/layer_factory.h

@@ -12,7 +12,7 @@
 #include "situation_map_types.h"
 #include <Common/situation_map_logging.h>
 
-#include <arcgis/arcgisversion.h>  // This file is created by RME, not ESRI
+#include <arcgisversion.h>  // This file is created by RME, not ESRI
 
 // Qt