fr: need a page on how MeshConfig works and how to manage it

[craigbox]

There are a number of features that require you to install Istio with a MeshConfig value set; all we have as documentation for this is https://istio.io/latest/docs/reference/config/istio.mesh.v1alpha1/.

We need to define at least answers to these in on istio.io:

(a) why v1alpha1?
(b) how should a user query these values?
(c) how can you find the defaults if no value is set?
(d) should you ever change it in the ConfigMap?
(e) is it generally safe to reinstall Istio to change these values?