Issue Description:

Tested with Swift 5.3.2 (Xcode 12.3, build 12C33)

Consider the following code:

import SwiftUI
 
struct MyScrollView: NSViewRepresentable {
}

Xcode suggests adding protocol stubs. If you use the fix-it, then it will add in typealias NSViewType = <#type#>.

If you don't write the type: Xcode will suggest adding protocol stubs and if you click Fix, it will add another typealias NSViewType = <#type#>.

If you do write the type, it will still suggest adding protocol stubs. If you click Fix, now it adds stubs for func makeNSView and func updateNSView.

It would be nice if:

1. We didn't add a duplicate stub in case there's an error (easy mistake to make if you're going too fast).

2. Add all the stubs at once, instead of going back-and-forth.