Update consul-k8s docs based on the consul-k8s release/1.0.x branch

[curtbushko]

Description

Updating the helm docs to capture some cleanups of wording for helm and to add the cni.namespace helm stanza to the docs.

Testing & Reproduction steps

• In the case of bugs, describe how to replicate
• If any manual tests were done, document the steps and the conditions to replicate
• Call out any important/ relevant unit tests, e2e tests or integration tests you have added or are adding

Links

The CNI Namespace PR hashicorp/consul-k8s#1756

PR Checklist

• updated test coverage
• external facing docs updated
• not a security concern