fix React-jsitooling build error for use_frameworks build (#50252)

Summary:
to resolve use_frameworks build error. this is an edge case happening only when there's objective-c files import to `React_RCTAppDelegate`. Xcode will have `include of non-modular header inside framework module` error originally. this is the generated umbrella header for jsitooling is incorrect. even the header path are correct, they are not modular headers.

~this pr adds a workaround to import header from outside the module.~ updates: this pr uses a forward declaration to prevent exposing the dependency in umbrella header.

[IOS] [FIXED] - `JSRuntimeFactoryCAPI.h` build error for  `use_frameworks` build

Pull Request resolved: https://github.com/facebook/react-native/pull/50252

Test Plan:
to reproduce the build error, we can build `USE_FRAMEWORKS=static bundle exec pod install` from rn-tester. we also need to import `React_RCTAppDelegate` from objective-c files. in this case, we can add `import React_RCTAppDelegate;` in rn-tester's main.m

```diff
 --- a/packages/rn-tester/RNTester/main.m
+++ b/packages/rn-tester/RNTester/main.m
@@ -8,6 +8,9 @@
 #import <UIKit/UIKit.h>

 #import "AppDelegate.h"
+@import React_RCTAppDelegate;
+// This also triggers the error
+//#import <React_RCTAppDelegate/React-RCTAppDelegate-umbrella.h>

 int main(int argc, char *argv[])
 {
```

Reviewed By: fabriziocucci

Differential Revision: D71963188

Pulled By: cipolleschi

fbshipit-source-id: 5d566ae5aadb9efc032aacfe32862ea289134f87

packages/react-native/Libraries/AppDelegate/RCTJSRuntimeConfiguratorProtocol.h

@@ -5,13 +5,14 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-#import <UIKit/UIKit.h>
-#import <react/runtime/JSRuntimeFactoryCAPI.h>
-
 #pragma once
 
 NS_ASSUME_NONNULL_BEGIN
 
+// Forward declarations for umbrella headers.
+// In implementations, import `<react/runtime/JSRuntimeFactoryCAPI.h>` to obtain the actual type.
+typedef void *JSRuntimeFactoryRef;
+
 @protocol RCTJSRuntimeConfiguratorProtocol
 
 - (JSRuntimeFactoryRef)createJSRuntimeFactory;

packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.mm

@@ -32,6 +32,7 @@
 #import <react/renderer/runtimescheduler/RuntimeScheduler.h>
 #import <react/renderer/runtimescheduler/RuntimeSchedulerCallInvoker.h>
 #import <react/runtime/JSRuntimeFactory.h>
+#import <react/runtime/JSRuntimeFactoryCAPI.h>
 
 @implementation RCTRootViewFactoryConfiguration
 

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

@@ -48,8 +48,11 @@ Pod::Spec.new do |s|
     s.header_mappings_dir  = "./"
   end
 
-  s.pod_target_xcconfig    = { "HEADER_SEARCH_PATHS" => header_search_paths.join(" "),
-                               "CLANG_CXX_LANGUAGE_STANDARD" => rct_cxx_language_standard() }
+  s.pod_target_xcconfig    = {
+    "HEADER_SEARCH_PATHS" => header_search_paths.join(" "),
+    "CLANG_CXX_LANGUAGE_STANDARD" => rct_cxx_language_standard(),
+    "DEFINES_MODULE" => "YES",
+  }
 
   s.dependency "React-cxxreact", version
   s.dependency "React-jsi", version

packages/react-native/ReactCommon/jsitooling/react/runtime/JSRuntimeFactory.h

@@ -7,6 +7,8 @@
 
 #pragma once
 
+#ifdef __cplusplus
+
 #include <ReactCommon/RuntimeExecutor.h>
 #include <cxxreact/MessageQueueThread.h>
 #include <jsi/jsi.h>
@@ -72,3 +74,5 @@ class JSIRuntimeHolder : public JSRuntime {
 };
 
 } // namespace facebook::react
+
+#endif // __cplusplus