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/Services/CentralEffectSimulation/Plugins/Explosions/expand_polygon.cpp

@@ -11,8 +11,8 @@
 
 #include <CentralEffectSimulation/logger.h>
 
-#include <arcgis/PolygonBuilder.h>
-#include <arcgis/GeometryEngine.h>
+#include <PolygonBuilder.h>
+#include <GeometryEngine.h>
 
 namespace CesExplosions
 {