Backport of add docs for consul-k8s config read command into release/1.15.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #17461 to be assessed for backporting due to the inclusion of the label backport/1.15.

🚨

Warning automatic cherry-pick of commits failed. If the first commit failed,
you will see a blank no-op commit below. If at least one commit succeeded, you
will see the cherry-picked commits up to, not including, the commit where
the merge conflict occurred.

The person who merged in the original PR is:
@david-yu
This person should manually cherry-pick the original PR into a new backport PR,
and close this one when the manual backport PR is merged in.

merge conflict error: unable to process merge commit: "4a22f34b599242962638bd0f85c054da6cdac30f", automatic backport requires rebase workflow

The below text is copied from the body of the original PR.

---

This PR adds documentation for the functionality introduced in hashicorp/consul-k8s#2078.

Description

Testing & Reproduction steps

Links

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

---

Overview of commits

• 6e53750 - fbdab01 - 4a22f34 - 54bcb95

[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR

[hanshasselberg]

This PR is fine as is -- only merge commits didn't make it in here.

[david-yu]

@hanshasselberg I can merge for you when 1.1.2 is released.

[hanshasselberg]

@david-yu sounds good, letting you merge this one. I will try to keep an eye out on the ent merge.