feat: improve RCTAppDelegate usage for brownfield

[okwasniewski]

Summary:

This PR improves the usage of RCTAppDelegate for brownfield scenarios.

Currently, when we want to integrate React Native with a brownfield app users might not want to initialize React Native in the main window. They may want to create it later.

Example usage:

class AppDelegate: RCTAppDelegate {
   override func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
      // Disable automatically creating react native window
      self.automaticallyLoadReactNativeWindow = false

      return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

import Foundation
import React
import React_RCTAppDelegate

class SettingsViewController: UIViewController {

  override func viewDidLoad() {
    super.viewDidLoad()
    self.view = (RCTSharedApplication()?.delegate as? RCTAppDelegate)?.rootViewFactory .view(withModuleName: "Settings", initialProperties: [:])
  }
}

Changelog:

[IOS] [ADDED] - improve RCTAppDelegate usage for brownfield, add automaticallyLoadReactNativeWindow flag

Test Plan:

CI Green

[cipolleschi]

Thanks for putting up this PR

[facebook-github-bot]

@cipolleschi has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@cipolleschi merged this pull request in 391680f.

[react-native-bot]

This pull request was successfully merged by @okwasniewski in 391680f

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