Inform user about onboarding status of gateways and stargates

[PodTheCoder]

Scenario:
User wants to join their device to the Edge Network. On create stake they select a Gateway / Stargate stake. They later discover these nodes are not (yet) available for onboarding. This causes confusion and prevents more people from contributing their computing.

Potential solutions:

• Add info box with onboarding status.
• Add warning when selecting a gateway or stargate.
• Add hover over hint about onboarding.
• Grey out gateways / stargates.
• ...