Backout "[RN] Fabric: Enable zIndex only for non-`static` positioned views"

Summary:
Changelog: [internal]

Backout D22098586 (476ab7481e) because of issues like D22843134 (799654b105).

[428](https://fburl.com/codesearch/0dyyakf5) places with zIndex and most of them do not have position defined. This could cause views to be overlapped.

Reviewed By: JoshuaGross

Differential Revision: D22890669

fbshipit-source-id: 200d1cbe2a4c27e2a0445b315868f37418ab1d9b

ReactCommon/react/renderer/components/view/ConcreteViewShadowNode.h

@@ -105,18 +105,13 @@ class ConcreteViewShadowNode : public ConcreteShadowNode<
   void initialize() noexcept {
     auto &props = BaseShadowNode::getConcreteProps();
 
+    BaseShadowNode::orderIndex_ = props.zIndex.value_or(0);
+
     if (props.yogaStyle.display() == YGDisplayNone) {
       BaseShadowNode::traits_.set(ShadowNodeTraits::Trait::Hidden);
     } else {
       BaseShadowNode::traits_.unset(ShadowNodeTraits::Trait::Hidden);
     }
-
-    // `zIndex` is only defined for non-`static` positioned views.
-    if (props.yogaStyle.positionType() != YGPositionTypeStatic) {
-      BaseShadowNode::orderIndex_ = props.zIndex.value_or(0);
-    } else {
-      BaseShadowNode::orderIndex_ = 0;
-    }
   }
 };
 

ReactCommon/react/renderer/components/view/ViewShadowNode.cpp

@@ -45,7 +45,7 @@ void ViewShadowNode::initialize() noexcept {
       viewProps.opacity != 1.0 || viewProps.transform != Transform{} ||
       viewProps.elevation != 0 ||
       (viewProps.zIndex.has_value() &&
-       viewProps.yogaStyle.positionType() != YGPositionTypeStatic) ||
+       viewProps.yogaStyle.positionType() != YGPositionTypeAbsolute) ||
       viewProps.yogaStyle.display() == YGDisplayNone ||
       viewProps.getClipsContentToBounds() ||
       isColorMeaningful(viewProps.shadowColor) ||