Fix SliverPersistentHeader interactions with SliverCrossAxisGroup (#127338)

This PR fixes `SliverCrossAxisGroup` so that once we calculate the total `scrollExtent` of the `SliverCrossAxisGroup`, we ensure that any child sliver is not painted outside of the "scroll extent" of the sliver group.

https://github.com/flutter/flutter/assets/2004742/670dc6f9-a3c6-4bcc-85d3-576cf7f33c6a

https://github.com/flutter/flutter/assets/2004742/0c9cd951-c133-4a8b-9e5e-89d0a69a4f59

Fixes #126958.
Fixes #126957.

packages/flutter/lib/src/rendering/sliver_group.dart

@@ -76,7 +76,6 @@ class RenderSliverCrossAxisGroup extends RenderSliver with ContainerRenderObject
     final double extentPerFlexValue = remainingExtent / totalFlex;
 
     child = firstChild;
-    double offset = 0.0;
 
     // At this point, all slivers with constrained cross axis should already be laid out.
     // Layout the rest and keep track of the child geometry with greatest scrollExtent.
@@ -94,22 +93,35 @@ class RenderSliverCrossAxisGroup extends RenderSliver with ContainerRenderObject
       } else {
         childExtent = child.geometry!.crossAxisExtent!;
       }
+      final SliverGeometry childLayoutGeometry = child.geometry!;
+      if (geometry!.scrollExtent < childLayoutGeometry.scrollExtent) {
+        geometry = childLayoutGeometry;
+      }
+      child = childAfter(child);
+    }
+
+    // Go back and correct any slivers using a negative paint offset if it tries
+    // to paint outside the bounds of the sliver group.
+    child = firstChild;
+    double offset = 0.0;
+    while (child != null) {
+      final SliverPhysicalParentData childParentData = child.parentData! as SliverPhysicalParentData;
+      final SliverGeometry childLayoutGeometry = child.geometry!;
+      final double remainingExtent = geometry!.scrollExtent - constraints.scrollOffset;
+      final double paintCorrection = childLayoutGeometry.paintExtent > remainingExtent
+        ? childLayoutGeometry.paintExtent - remainingExtent
+        : 0.0;
+      final double childExtent = child.geometry!.crossAxisExtent ?? extentPerFlexValue * (childParentData.crossAxisFlex ?? 0);
       // Set child parent data.
       switch (constraints.axis) {
         case Axis.vertical:
-          childParentData.paintOffset = Offset(offset, 0.0);
+          childParentData.paintOffset = Offset(offset, -paintCorrection);
         case Axis.horizontal:
-          childParentData.paintOffset = Offset(0.0, offset);
+          childParentData.paintOffset = Offset(-paintCorrection, offset);
       }
       offset += childExtent;
-      if (geometry!.scrollExtent < child.geometry!.scrollExtent) {
-        geometry = child.geometry;
-      }
       child = childAfter(child);
     }
-
-    // Set the geometry with the proper crossAxisExtent.
-    geometry = geometry!.copyWith(crossAxisExtent: constraints.crossAxisExtent);
   }
 
   @override