Backport of docs: install consul-cni manually or via linux packaging into release/1.8.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #23322 to be assessed for backporting due to the inclusion of the label backport/1.8.x.

🚨

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: "0cc2ab5ae96f96fb29e97937936476863dca08b4", automatic backport requires rebase workflow

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

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Install the consul-cni plugin via apt or yum.

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Overview of commits

• 0cc2ab5

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