Add support for display: contents (#46584)

Summary:
This PR adds support for `display: contents` style by effectively skipping nodes with `display: contents` set during layout.

This required changes in the logic related to children traversal - before this PR a node would be always laid out in the context of its direct parent. After this PR that assumption is no longer true - `display: contents` allows nodes to be skipped, i.e.:

```html
<div id="node1">
  <div id="node2" style="display: contents;">
    <div id="node3" />
  </div>
</div>
```

`node3` will be laid out as if it were a child of `node1`.

Because of this, iterating over direct children of a node is no longer correct to achieve the correct layout. This PR introduces `LayoutableChildren::Iterator` which can traverse the subtree of a given node in a way that nodes with `display: contents` are replaced with their concrete children.

A tree like this:
```mermaid
flowchart TD
    A((A))
    B((B))
    C((C))
    D((D))
    E((E))
    F((F))
    G((G))
    H((H))
    I((I))
    J((J))

    A --> B
    A --> C
    B --> D
    B --> E
    C --> F
    D --> G
    F --> H
    G --> I
    H --> J

    style B fill:#50
    style C fill:#50
    style D fill:#50
    style H fill:#50
    style I fill:#50
```

would be laid out as if the green nodes (ones with `display: contents`) did not exist. It also changes the logic where children were accessed by index to use the iterator instead as random access would be non-trivial to implement and it's not really necessary - the iteration was always sequential and indices were only used as boundaries.

There's one place where knowledge of layoutable children is required to calculate the gap. An optimization for this is for a node to keep a counter of how many `display: contents` nodes are its children. If there are none, a short path of just returning the size of the children vector can be taken, otherwise it needs to iterate over layoutable children and count them, since the structure may be complex.

One more major change this PR introduces is `cleanupContentsNodesRecursively`. Since nodes with `display: contents` would be entirely skipped during the layout pass, they would keep previous metrics, would be kept as dirty, and, in the case of nested `contents` nodes, would not be cloned, breaking `doesOwn` relation. All of this is handled in the new method which clones `contents` nodes recursively, sets empty layout, and marks them as clean and having a new layout so that it can be used on the React Native side.

Relies on facebook/yoga#1725

X-link: facebook/yoga#1726

This PR adds a few things over the corresponding one in Yoga:
- new value in the `DisplayType` enum - `Contents`
- new `ShadowNodeTrait` - `ForceFlattenView`, that forces the node not to form a host view
- updates TS types to include `display: contents`
- aliases `display: contents` to `display: none` on the old architecture

## Changelog:

[GENERAL] [ADDED] - Added support for `display: contents`

Pull Request resolved: #46584

Test Plan:
<details>
<summary>So far I've been testing on relatively simple snippets like this one and on entirety of RNTester by inserting views with `display: contents` in random places and seeing if anything breaks.</summary>

```jsx
import React from 'react';
import { Button, Pressable, SafeAreaView, ScrollView, TextInput, View, Text } from 'react-native';

export default function App() {
  const [toggle, setToggle] = React.useState(false);
  return (
    <View style={{flex: 1, paddingTop: 100}}>
      <SafeAreaView style={{width: '100%', height: 200}}>
        <Pressable style={{width: 100, height: 100, backgroundColor: 'black'}} onPress={() => setToggle(!toggle)}>
          <ScrollView />
        </Pressable>
        <View style={{display: 'flex', flexDirection: 'row', flex: 1, backgroundColor: 'magenta'}}>
          <SafeAreaView style={{
            // display: 'contents',
            flex: 1,
            }}>
            <View style={{
              display: 'contents',
              width: '100%',
              height: 200,
              }}>
              <View style={{
                  display: 'contents',
                  flex: 1,
                }}>
                { toggle && <View style={{flex: 1, backgroundColor: 'yellow'}} /> }
                <View style={{flex: 1, backgroundColor: 'blue'}} />
                <View style={{flex: 1, backgroundColor: 'cyan'}} />
              </View>
            </View>
          </SafeAreaView>
        </View>
        {/* <View style={{width: 100, height: 100, backgroundColor: 'magenta', display: 'flex'}} /> */}
        <TextInput style={{width: 200, height: 100, backgroundColor: 'red', display: 'flex'}}>
          <Text style={{color: 'white'}}>Hello</Text>
          <Text style={{color: 'green'}}>World</Text>
        </TextInput>
      </SafeAreaView>
    </View>
  );
}
```

</details>

Reviewed By: joevilches

Differential Revision: D64584476

Pulled By: NickGerleman

fbshipit-source-id: bec77b5087ff95f0980cf02274fbb2c8581eb3c0

Author: j-piasecki

packages/react-native/Libraries/StyleSheet/StyleSheetTypes.d.ts

@@ -56,7 +56,7 @@ export interface FlexStyle {
   borderWidth?: number | undefined;
   bottom?: DimensionValue | undefined;
   boxSizing?: 'border-box' | 'content-box' | undefined;
-  display?: 'none' | 'flex' | undefined;
+  display?: 'none' | 'flex' | 'contents' | undefined;
   end?: DimensionValue | undefined;
   flex?: number | undefined;
   flexBasis?: DimensionValue | undefined;

packages/react-native/Libraries/StyleSheet/StyleSheetTypes.js

@@ -58,7 +58,7 @@ type ____LayoutStyle_Internal = $ReadOnly<{
    *  It works similarly to `display` in CSS, but only support 'flex' and 'none'.
    *  'flex' is the default.
    */
-  display?: 'none' | 'flex',
+  display?: 'none' | 'flex' | 'contents',
 
   /** `width` sets the width of this component.
    *

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -7927,7 +7927,7 @@ export type DimensionValue = number | string | \\"auto\\" | AnimatedNode | null;
 export type AnimatableNumericValue = number | AnimatedNode;
 export type CursorValue = \\"auto\\" | \\"pointer\\";
 type ____LayoutStyle_Internal = $ReadOnly<{
-  display?: \\"none\\" | \\"flex\\",
+  display?: \\"none\\" | \\"flex\\" | \\"contents\\",
   width?: DimensionValue,
   height?: DimensionValue,
   bottom?: DimensionValue,

packages/react-native/ReactCommon/react/renderer/components/view/YogaLayoutableShadowNode.cpp

@@ -388,6 +388,12 @@ void YogaLayoutableShadowNode::updateYogaProps() {
         !viewProps.filter.empty();
     YGNodeSetAlwaysFormsContainingBlock(&yogaNode_, alwaysFormsContainingBlock);
   }
+
+  if (yogaNode_.style().display() == yoga::Display::Contents) {
+    ShadowNode::traits_.set(ShadowNodeTraits::ForceFlattenView);
+  } else {
+    ShadowNode::traits_.unset(ShadowNodeTraits::ForceFlattenView);
+  }
 }
 
 /*static*/ yoga::Style YogaLayoutableShadowNode::applyAliasedProps(

packages/react-native/ReactCommon/react/renderer/components/view/conversions.h

@@ -439,6 +439,10 @@ inline void fromRawValue(
     result = yoga::Display::None;
     return;
   }
+  if (stringValue == "contents") {
+    result = yoga::Display::Contents;
+    return;
+  }
   LOG(ERROR) << "Could not parse yoga::Display: " << stringValue;
 }
 

packages/react-native/ReactCommon/react/renderer/core/ShadowNodeTraits.h

@@ -75,6 +75,9 @@ class ShadowNodeTraits {
 
     // Inherits `YogaLayoutableShadowNode` and has a custom baseline function.
     BaselineYogaNode = 1 << 10,
+
+    // Forces the node not to form a host view.
+    ForceFlattenView = 1 << 11,
   };
 
   /*

packages/react-native/ReactCommon/react/renderer/mounting/Differentiator.cpp

@@ -245,13 +245,17 @@ static void sliceChildShadowNodeViewPairsRecursively(
     // shuffling their children around.
     bool childrenFormStackingContexts = shadowNode.getTraits().check(
         ShadowNodeTraits::Trait::ChildrenFormStackingContext);
-    bool isConcreteView =
-        childShadowNode.getTraits().check(ShadowNodeTraits::Trait::FormsView) ||
-        childrenFormStackingContexts;
-    bool areChildrenFlattened =
+    bool isConcreteView = (childShadowNode.getTraits().check(
+                               ShadowNodeTraits::Trait::FormsView) ||
+                           childrenFormStackingContexts) &&
         !childShadowNode.getTraits().check(
-            ShadowNodeTraits::Trait::FormsStackingContext) &&
-        !childrenFormStackingContexts;
+            ShadowNodeTraits::Trait::ForceFlattenView);
+    bool areChildrenFlattened =
+        (!childShadowNode.getTraits().check(
+             ShadowNodeTraits::Trait::FormsStackingContext) &&
+         !childrenFormStackingContexts) ||
+        childShadowNode.getTraits().check(
+            ShadowNodeTraits::Trait::ForceFlattenView);
 
     Point storedOrigin = {};
     if (areChildrenFlattened) {