Update Docs - Project Network Isolation

[sunilarjun]

We have multiple comments in slack (one such posted below) that refer to the lack of documentation on Project Network Isolation (PNI) in Rancher docs. I've looked through the documentation and found a couple pages where PNI is mentioned, but need expanding on information as to what PNI is, how it works, and why a user would need it.

Project Network Isolation in Rancher Docs reference:

• https://ranchermanager.docs.rancher.com/integrations-in-rancher/istio/configuration-options/project-network-isolation
• https://ranchermanager.docs.rancher.com/reference-guides/cluster-configuration/rancher-server-configuration/rke1-cluster-configuration#project-network-isolation
• https://ranchermanager.docs.rancher.com/reference-guides/cluster-configuration/rancher-server-configuration/rke2-cluster-configuration#project-network-isolation
• https://ranchermanager.docs.rancher.com/reference-guides/cluster-configuration/rancher-server-configuration/rke2-cluster-configuration#container-network-provider

Slack comment 08/26/24:

I think this got mentioned a couple of times. But shouldn´t we have a documentation page on Project Network Isolation (PNI)? It feels like there is almost no information at all on it, and every time a customer asks about it, I need to run it on a lab to explain what it does, how and why.