feat(visionos): support for xros platform

[NathanWalker]

• Splits the ios and vision templates and builds them independently via npm run build-ios and npm run build-vision
• Allows an optional conditional app boot style between Objective C or SwiftUI, enabled by default on visionOS and can optionally be enabled on iOS apps with the following:

1. set build.xcconfig:

NS_SWIFTUI_BOOT  = 1

2. Add App_Resources/iOS/src/NativeScriptApp.swift with the following:

import SwiftUI

@main
struct NativeScriptApp: App {

    var body: some Scene {
        NativeScriptMainWindow()
    }
}

3. Enable embedded flag on boot, for example in Angular apps it can be enabled with:

runNativeScriptAngularApp({
  embedded: true, // <-- this enables embedded mode
  appModuleBootstrap: () => platformNativeScript().bootstrapModule(AppModule),
});