Backport of [release/1.15.3] Add cloud stanza documentation into release/1.14.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #17311 to be assessed for backporting due to the inclusion of the label backport/1.14.

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The person who merged in the original PR is:
@hanshasselberg
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: POST https://api.github.com/repos/hashicorp/consul/merges: 409 Merge conflict []

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

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Description

This PR adds documentation for the HCP cloud stanza.

PR Checklist

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

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Overview of commits

• 39e273a - f563ed0 - 53b0ee9

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

Auto approved Consul Bot automated PR