[IOT][SYSTEMD] Improve Astarte message hub integration and systemd network initialization

This merge request introduces targeted improvements to the integration of astarte-message-hub and optimizes the behavior of systemd-networkd-wait-online to enhance system responsiveness and service reliability.

Summary of Changes

• Astarte Message Hub:
  • Downgraded to version 0.5.4 to ensure compatibility and stability.
  • Replaced SRC_URI to use a Git source for improved revision control.
  • Updated the default gRPC port to 50051 in the service configuration.
  • Adjusted the path parameter to align with deployment requirements.
• Systemd Configuration:
  • Added an override for systemd-networkd-wait-online.service to include the --any flag.
    • This allows the system to proceed once any network interface is online, improving boot time on devices with multiple interfaces.