Add support for custom percentiles in ensemble statistics

Introduced custom percentile handling for ensemble statistics:
- Added "CUSTOM" statistics type and percentile field to RifEclipseSummaryAddress
- Refactored RimEnsembleStatisticsCase to store and compute arbitrary percentiles
- RimEnsembleStatistics now parses custom percentiles from UI input
- RimEnsembleCurveSet and related interfaces updated to handle custom percentile curves and labels
- Hashing and statistics calculations now include custom percentiles for cache validity

ApplicationLibCode/ProjectDataModel/WellLog/RimEnsembleWellLogCurveSet.cpp

@@ -1088,6 +1088,15 @@ bool RimEnsembleWellLogCurveSet::hasMeanData() const
     return m_ensembleWellLogStatistics->hasMeanData();
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+bool RimEnsembleWellLogCurveSet::hasPercentileData( int /*p*/ ) const
+{
+    // Custom percentiles are not supported for well log statistics
+    return false;
+}
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------

ApplicationLibCode/ProjectDataModel/WellLog/RimEnsembleWellLogCurveSet.h

@@ -108,6 +108,7 @@ public:
     bool hasP50Data() const override;
     bool hasP90Data() const override;
     bool hasMeanData() const override;
+    bool hasPercentileData( int p ) const override;
 
     void appendColorGroup( caf::PdmUiOrdering& uiOrdering );