Doc: Initial iteration of Kubernetes Dashboard in Environment page

What does this MR do and why?

This MR adds documentations for Initial iteration of Kubernetes Dashboard in En... (&9859 - closed), which includes the following changes:

• Document how to setup and use "Kubernetes Dashboard in Environment pages", as deployment project members.
• Document how to setup user_access keyword and Kubernetes RBAC, as agent administrator.
• Move similar but deprecated topics to deprecated_features.md. This way, it's easier for users to land on the kubernetes_dashaboard.md page.

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