Pulling container images. Different commands required for Agent v2 and v3

[mjang]

Overview

Current doc, at least here, is misleading.

Description

It specifies VERSION_TAG as a label for a distro

Related: we now support two different agents, v2 and v3

We need to change the linked doc (and possibly others) to:

---

I think we need to make it completely obvious in the documentation that :

• Agent V2
  docker pull private-registry.nginx.com/nginx-plus/agent:{DISTRO}
• Agent V3 - For N1C, this is the one that unlocks the new features such as otel metrics back to the console, NAP, and UWAAP in XC (soon)
  docker pull private-registry.nginx.com/nginx-plus/agentv3:{DISTRO}

---

As noted by @mattdesmarais

Probably also affected:

• https://docs.nginx.com/nginx-one/connect-instances/connect-nginx-plus-container-images-to-nginx-one/
• https://docs.nginx.com/nginx-one/nginx-configs/config-sync-groups/manage-config-sync-groups/
• https://docs.nginx.com/nginx/admin-guide/installing-nginx/installing-nginx-docker/#use-official-nginx-plus-docker-images

Acceptance criteria

Review all doc content where we use docker to pull different distro images, and have to specify options for different agents