PoC: NGINX Plus support with agent

[sjberman]

As a maintainer of NGF
I want to do an early prototype of NGF integrating with NGINX Agent using NGINX Plus
So that I can give the Agent team feedback for integration in preparation for data and control plane separation.

Expanding on the work done in: #1679

Acceptance

• An NGF environment is created that integrates with NGINX Agent using NGINX Plus.
• Feedback on Agent integration is relayed to the NGINX Agent team.

[sjberman]

The work to set this PoC up is just going to overlap the work in this epic to build everything else. We're not really going to be able to get a head start on testing out NGINX Plus without doing the rest of the work in the epic anyway, so I'm closing this.