[fabric] Disable view flattening in VirtualizedList cells

Summary:
Scroll views set up with an inverted vertical axis can't support view flattening due to the flattening not taking the axis inversion in consideration while repositioning the views.

This diff disables view flattening on the cells of the virtualized list so that the layout would be correct in inverted scroll views when using Fabric.

The change is not being applied to ScrollView directly because we can safely assume that vertical axis inversion will only be enabled on VirtualizedList/FlatList.

Test Plan:
Run Zeratul with Fabric and check that the vertical order of grouped bubble messages is correct.

| Before | After |
|--|
|  {F1136386200}  |  {F1136386364}  |

Reviewers: shawndempsey, #rn-desktop

Reviewed By: shawndempsey

Differential Revision: https://phabricator.intern.facebook.com/D50846483

Tasks: T167539420

Author: Nick Lefever

packages/virtualized-lists/Lists/VirtualizedListCellRenderer.js

@@ -19,7 +19,7 @@ import type {
 import {VirtualizedListCellContextProvider} from './VirtualizedListContext.js';
 import invariant from 'invariant';
 import * as React from 'react';
-import {StyleSheet, View} from 'react-native';
+import {Platform, StyleSheet, View} from 'react-native'; // [macOS]
 
 export type Props<ItemT> = {
   CellRendererComponent?: ?React.ComponentType<CellRendererProps<ItemT>>,
@@ -219,7 +219,7 @@ export default class CellRenderer<ItemT> extends React.PureComponent<
       : horizontal
         ? [styles.row, inversionStyle]
         : inversionStyle;
-    const result = !CellRendererComponent ? (
+    let result = !CellRendererComponent ? ( // [macOS]
       <View
         style={cellStyle}
         onFocusCapture={this._onCellFocusCapture}
@@ -240,6 +240,11 @@ export default class CellRenderer<ItemT> extends React.PureComponent<
       </CellRendererComponent>
     );
 
+    if (Platform.OS === 'macos') {
+      // [macOS
+      result = React.cloneElement(result, {collapsable: false});
+    } // macOS]
+
     return (
       <VirtualizedListCellContextProvider cellKey={this.props.cellKey}>
         {result}