#12495 Refactors ensemble statistics handling

Removes the dedicated `SUMMARY_ENSEMBLE_STATISTICS` category and instead uses a `statisticsType` field within `RifEclipseSummaryAddress` to represent ensemble statistics.

This change simplifies the code and avoids potential confusion by representing statistics as attributes of existing summary types, rather than a separate category. It also improves code robustness.

ApplicationLibCode/ProjectDataModel/Summary/RimEnsembleCrossPlotStatisticsCase.cpp

@@ -49,16 +49,19 @@ std::pair<bool, std::vector<double>> RimEnsembleCrossPlotStatisticsCase::values(
         }
     }
 
-    auto quantityName = resultAddress.ensembleStatisticsVectorName();
-
-    if ( quantityName == RifEclipseSummaryAddressDefines::statisticsNameP10() )
-        return { true, m_p10Data };
-    else if ( quantityName == RifEclipseSummaryAddressDefines::statisticsNameP50() )
-        return { true, m_p50Data };
-    else if ( quantityName == RifEclipseSummaryAddressDefines::statisticsNameP90() )
-        return { true, m_p90Data };
-    else if ( quantityName == RifEclipseSummaryAddressDefines::statisticsNameMean() )
-        return { true, m_meanData };
+    switch ( resultAddress.statisticsType() )
+    {
+        case RifEclipseSummaryAddressDefines::StatisticsType::P10:
+            return { true, m_p10Data };
+        case RifEclipseSummaryAddressDefines::StatisticsType::P50:
+            return { true, m_p50Data };
+        case RifEclipseSummaryAddressDefines::StatisticsType::P90:
+            return { true, m_p90Data };
+        case RifEclipseSummaryAddressDefines::StatisticsType::MEAN:
+            return { true, m_meanData };
+        default:
+            break;
+    }
 
     return { true, {} };
 }