[macOS] Implement native system network extensions

[teon]

As we want to publish the client through the App Store, we need to implement native Swift system network extensions.

• Research and docs about Rust -> Swift integration
• Send tunnel information to Swift code.
• Load/save tunnel settings (for every location)
• Find a way to communicate from Swift to Rust (Tauri) – status and statistics
• Discover why NETunnelProviderSession.sendProviderMessage does not work from defguard-client
• Build Defguard Client app bundle in CI, including the network extension
• Fix initial connection issues

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• Sync Defguard tunnels with System Setting
• Statistics and VPN status from system to Desktop
• Stop using /var/log/defguard-service for logging.