Remove deprecated size_t overloads from RigActiveCellInfo

Migrate all callers to use type-safe ReservoirCellIndex and
ActiveCellIndex wrappers, then remove the deprecated isActive(size_t),
cellResultIndex(size_t), and setCellResultIndex(size_t, size_t) methods.

ApplicationLibCode/SocketInterface/RiaCaseInfoCommands.cpp

@@ -208,7 +208,7 @@ public:
 
         for ( size_t cIdx = 0; cIdx < mainGrid->totalCellCount(); ++cIdx )
         {
-            if ( actCellInfo->isActive( cIdx ) )
+            if ( actCellInfo->isActive( ReservoirCellIndex( cIdx ) ) )
             {
                 auto&        cell = mainGrid->cell( cIdx );
                 RigGridBase* grid = cell.hostGrid();