Add KonnectExtension to ControlPlane and GatewayConfiguration

[mlavacca]

Problem Statement

During #453, the attachment of KonnectExtension to the GatewayConfiguration was explored, but it resulted in something more complex than just barely putting the extension field to the GatewayConfiguration and propagating it to the DataPlane.

If we provision the DataPlane with Konnect configuration and a regular ControlPlane, we end up with KIC not being able to push configuration to the DataPlane (as it is not configured to accept the config from KIC), and it never gets ready.

Proposed Solution

We likely need to improve the Controlplane as well to be able to receive KonnectExtension, to configure it to work in Konnect.

Acceptance Criteria

• As a user, I can create a Gateway and make it completely configured on Konnect, by means of the KonnectExtension API