Enhances ensemble curve handling and performance

* Removes obsolete code
* Return first non-empty return value from reader
* Simplifies water cut curve visibility check
* Defers the page update until after all plots have been added.
* Add settings to control number of threads
* Refactors ensemble curve handling and visibility

Improves the efficiency of ensemble curve set management by separating realization and statistics curves into distinct collections. This allows for more targeted operations, such as selectively showing/hiding realization curves without affecting statistics.
Also defers data loading of curves until they are actually displayed, optimizing performance.
The visibility updates are modified to optionally skip updating the parent plot, providing more control over replotting behavior and preventing unnecessary updates.

ApplicationLibCode/Application/RiaApplication.cpp

@@ -30,6 +30,7 @@
 #include "RiaFontCache.h"
 #include "RiaImportEclipseCaseTools.h"
 #include "RiaLogging.h"
+#include "RiaOpenMPTools.h"
 #include "RiaPlotWindowRedrawScheduler.h"
 #include "RiaPreferences.h"
 #include "RiaPreferencesOsdu.h"
@@ -1590,6 +1591,12 @@ void RiaApplication::initialize()
     caf::SelectionManager::instance()->setPdmRootObject( project() );
 
     initializeDataLoadController();
+
+    const auto& [enabled, maxThreads] = RiaPreferencesSystem::current()->maximumNumberOfThreads();
+    if ( enabled )
+    {
+        RiaOpenMPTools::setMaxThreads( maxThreads );
+    }
 }
 
 //--------------------------------------------------------------------------------------------------