Secure connection between agent and control plane

[mpstefan]

As a user of NGF
I want the connection between the control and data plane to be secured with TLS
So that any changes to the data plane are encrypted.

Acceptance

• Any traffic between the control plane and Agent is encrypted.
  • By default, NGF can provide self-signed certs that are generated at installation time.
  • Docs should recommend that a customer use cert-manager in a production environment (with details on how to set this up).
• The agent should use a Bound Kubernetes ServiceAccount token to authenticate with the control plane.

Dev Notes

• https://github.com/nginx/nginx-gateway-fabric/tree/main/docs/proposals/control-data-plane-split#encryption
• Track agent connections using token uuid instead of IP address