Upgrade Root visibility to "for frameworks"

Summary:
Reclassifies `react/renderer/components/root:root` from public to "for frameworks" under the C++ stable API three-tier visibility model.

Consumers that opt into `RN_STRICT_API` now get a suppressible warning where they previously got an error pointing at the umbrella, and can acknowledge it with `RN_ALLOW_FRAMEWORKS`; without that flag the guards are inert, so no existing build changes behaviour.

Changelog: [Internal]

Differential Revision: D118440376

Author: j-piasecki

packages/react-native/ReactAndroid/build.gradle.kts

@@ -184,10 +184,6 @@ val preparePrefab by
                           "../ReactCommon/react/renderer/components/root/",
                           "react/renderer/components/root/",
                       ),
-                      Pair(
-                          "../ReactCommon/react/renderer/components/root/React/",
-                          "React/",
-                      ),
                       // runtimeexecutor
                       Pair("../ReactCommon/runtimeexecutor/", ""),
                       // react_renderer_textlayoutmanager

packages/react-native/ReactCommon/React-Fabric.podspec

@@ -134,16 +134,10 @@ Pod::Spec.new do |s|
   s.subspec "components" do |ss|
     ss.subspec "root" do |sss|
       sss.source_files         = podspec_sources("react/renderer/components/root/**/*.{m,mm,cpp,h}", "react/renderer/components/root/**/*.{h}")
-      sss.exclude_files        = ["react/renderer/components/root/tests", "react/renderer/components/root/React"]
+      sss.exclude_files        = "react/renderer/components/root/tests"
       sss.header_dir           = "react/renderer/components/root"
     end
 
-    ss.subspec "rootUmbrella" do |sss|
-      sss.source_files         = "react/renderer/components/root/React/*.h"
-      sss.header_dir           = ""
-      sss.header_mappings_dir  = "react/renderer/components/root"
-    end
-
     ss.subspec "view" do |sss|
       sss.dependency             "React-renderercss"
       sss.dependency             "Yoga"

packages/react-native/ReactCommon/react/renderer/components/root/React/Root.h

@@ -7,7 +7,7 @@
 
 #pragma once
 
-#include <react/cxxstableapi/UmbrellaGuard.h>
+#include <react/cxxstableapi/FrameworksGuard.h>
 
 #include <react/renderer/components/root/RootShadowNode.h>
 #include <react/renderer/core/ConcreteComponentDescriptor.h>

packages/react-native/ReactCommon/react/renderer/components/root/RootComponentDescriptor.h

@@ -7,7 +7,7 @@
 
 #pragma once
 
-#include <react/cxxstableapi/UmbrellaGuard.h>
+#include <react/cxxstableapi/FrameworksGuard.h>
 
 #include <memory>
 

packages/react-native/ReactCommon/react/renderer/components/root/RootProps.h

@@ -7,7 +7,7 @@
 
 #pragma once
 
-#include <react/cxxstableapi/UmbrellaGuard.h>
+#include <react/cxxstableapi/FrameworksGuard.h>
 
 #include <memory>
 

packages/react-native/ReactCommon/react/renderer/components/root/RootShadowNode.h

@@ -110,18 +110,9 @@ const PodspecExceptions /*: {[key: string]: PodSpecConfiguration} */ = {
           {
             name: 'root',
             headerPatterns: ['react/renderer/components/root/**/*.h'],
-            excludePatterns: [
-              'react/renderer/components/root/tests',
-              'react/renderer/components/root/React',
-            ],
+            excludePatterns: ['react/renderer/components/root/tests'],
             headerDir: 'react/renderer/components/root',
           },
-
-          {
-            name: 'rootUmbrella',
-            headerPatterns: ['react/renderer/components/root/React/*.h'],
-            headerDir: 'React',
-          },
           {
             name: 'view',
             headerPatterns: [