Fix RCT_NEW_ARCH_ENABLED for rn-macOS (#1779)

In rn-macOS 0.71 we have
https://github.com/microsoft/react-native-macos/tree/main/Libraries/AppDelegate
which pass the necessary RCT_NEW_ARCH_ENABLED flag to it's .h and .mm files
https://github.com/microsoft/react-native-macos/blob/main/Libraries/AppDelegate/React-RCTAppDelegate.podspec#L24

We also have:
https://github.com/microsoft/react-native-macos/tree/main/React/AppSetup
which DO NOT pass RCT_NEW_ARCH_ENABLED flag because it gets inherited from:
https://github.com/microsoft/react-native-macos/blob/main/React-Core.podspec

Instead of fixing the latter .podspec we just carry over a more recent rn 0.72 change > moving all files into the same folder / podspec
https://github.com/facebook/react-native/tree/main/packages/react-native/Libraries/AppDelegate

Author: christophpurrer

Libraries/AppDelegate/RCTAppDelegate.mm

@@ -6,7 +6,7 @@
  */
 
 #import "RCTAppDelegate.h"
-#import <React/RCTAppSetupUtils.h>
+#import "RCTAppSetupUtils.h"
 #import <React/RCTRootView.h>
 
 #if RCT_NEW_ARCH_ENABLED