Improve source result iteration efficiency

src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultDocument.Text.cs

@@ -269,6 +269,9 @@ internal Cursor GetEndIndex(Cursor cursor, bool includeEndElement)
         return endId;
     }
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal DbRow GetDbRow(Cursor cursor) => _parsedData.Get(cursor);
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static int GetEndRowLength(DbRow endRow)
         => endRow.TokenType is JsonTokenType.EndObject or JsonTokenType.EndArray

src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.ArrayEnumerator.cs

@@ -101,7 +101,9 @@ public bool MoveNext()
 
             // Already on an element: jump to just after this element (exclusive),
             // which is the start of the next element if one exists.
-            var next = _target._parent.GetEndIndex(_current, includeEndElement: true);
+            // Inlined from GetEndIndex(_current, includeEndElement: true).
+            var row = _target._parent.GetDbRow(_current);
+            var next = row.IsSimpleValue ? _current + 1 : _current + row.NumberOfRows;
 
             if (next < _endCursor)
             {

src/HotChocolate/Fusion/src/Fusion.Execution/Text/Json/SourceResultElement.ObjectEnumerator.cs

@@ -110,12 +110,13 @@ public bool MoveNext()
                 }
             }
 
-            // Advance past the current VALUE to the start of the next element.
-            // GetEndIndex(current, includeEndElement: true) yields the row after the current value.
-            var afterCurrent = _target._parent.GetEndIndex(_current, includeEndElement: true);
+            // Advance past the current VALUE to the row after it.
+            // Inlined from GetEndIndex(_current, includeEndElement: true) to avoid
+            // the method call overhead, disposed check, and branch on every iteration.
+            var row = _target._parent.GetDbRow(_current);
+            var afterCurrent = row.IsSimpleValue ? _current + 1 : _current + row.NumberOfRows;
 
-            // After a value, the next row (if any) is the next PropertyName; we need the VALUE,
-            // so we skip one more row.
+            // After the value comes the next PropertyName; skip it to reach the VALUE.
             var nextValue = afterCurrent + 1;
 
             if (nextValue < _endCursor)