Investigate why app & system extension shared dependencies fail to embed

In both #145 and #98, I've encountered an issue with release builds of the app. These issues arose when a dependency was required by both the App target (or any of it's dependencies), and the system extension target (and any of it's dependencies).

In #98, the issue occurred when protobuf definitions were added directly to the app target, or a new framework target that would be depended on by the app target. They were previously working fine being depended on by just `VPNLib` (which the system extension depends on).
In the first case, the network extension would crash. In the second case, the app would crash.
The crash reason was:
```
Library not loaded: @rpath/SwiftProtobuf.framework/Versions/A/SwiftProtobuf
```

Other users have reported this issue https://github.com/apple/swift-protobuf/issues/1506#issuecomment-2435125065

In #143, the issue occured when `InternalCollectionsUtilities` was depended on by both the App target, and the VPN target (via another framework, VPNLib). When a library that depended on `swift-collections` was added to the app target, the network extension would crash on startup with the error:
```
Library not loaded: @rpath/InternalCollectionsUtilities.framework/Versions/A/InternalCollectionsUtilities
```

FWICT, xcode is making some form of optimisation where it constructs a framework for code shared between two different targets. This poses an issue with a system extension, which is copied and executed outside of the app bundle. A copy of the system extension always lives in the app bundle, so it's trivial for the app to depend on a framework present within the system extension bundle (we already do this), but not the other way around. If there was some way to tell xcode to embed this new framework within the system extension bundle, we wouldn't have this issue.

Instead, the workaround we've gone with is to simply put everything that would cause this issue in `VPNLib`, as to minimise the number of times we depend on any one package.

This issue doesn't require immediate action, and is more so for book-keeping. It would be good to post this alongside an MRE on the Apple developer forums and in Apple feedback assistant.

Commencez par reproduire les échecs du build de release décrits dans les issues #145, #98 et #143, en vous concentrant sur les dépendances partagées par les targets d’extensions système App et VPN. Préparez un exemple minimal reproductible montrant le framework intégré manquant, puis documentez le résultat pour les Apple Developer Forums et Feedback Assistant comme indiqué dans l’issue.

Rédigé par le modèle d'indexation à partir du texte de l'issue.