Backport of Add -output-format json to consul-k8s proxy list command into release/1.2.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #3221 to be assessed for backporting due to the inclusion of the label backport/1.2.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:
@absolutelightning
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: "f214f2533a10a224f44e15ae42e1a498a7fc353d", automatic backport requires rebase workflow

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

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Changes proposed in this PR:

Add -output-format json to consul-k8s proxy list command. Only option now supported is json. If json is not set it defaults to table. Fixes - #2012

How I've tested this PR:

asheshvidyut@asheshvidyut-H2GX766V9T self-managed/local (NET-5259 *%) » consul-k8s proxy list -o json 
Namespace: default

[
    {
        "Name": "frontend-6fd97b8fb5-spqb8",
        "Type": "Sidecar"
    },
    {
        "Name": "nginx-6d7469694f-p5wrz",
        "Type": "Sidecar"
    },
    {
        "Name": "payments-667d87bf95-ktb8n",
        "Type": "Sidecar"
    },
    {
        "Name": "product-api-7c4d77c7c9-g4g2b",
        "Type": "Sidecar"
    },
    {
        "Name": "product-api-db-685c844cb-k5l8f",
        "Type": "Sidecar"
    },
    {
        "Name": "public-api-567d949866-cgksl",
        "Type": "Sidecar"
    }
]
asheshvidyut@asheshvidyut-H2GX766V9T self-managed/local (NET-5259 *%) »

asheshvidyut@asheshvidyut-H2GX766V9T self-managed/local (NET-5259 *%) » consul-k8s proxy list -o json -A
Namespace: all namespaces

[
    {
        "Name": "frontend-6fd97b8fb5-spqb8",
        "Namespace": "default",
        "Type": "Sidecar"
    },
    {
        "Name": "nginx-6d7469694f-p5wrz",
        "Namespace": "default",
        "Type": "Sidecar"
    },
    {
        "Name": "payments-667d87bf95-ktb8n",
        "Namespace": "default",
        "Type": "Sidecar"
    },
    {
        "Name": "product-api-7c4d77c7c9-g4g2b",
        "Namespace": "default",
        "Type": "Sidecar"
    },
    {
        "Name": "product-api-db-685c844cb-k5l8f",
        "Namespace": "default",
        "Type": "Sidecar"
    },
    {
        "Name": "public-api-567d949866-cgksl",
        "Namespace": "default",
        "Type": "Sidecar"
    }
]

How I expect reviewers to test this PR:

Checklist:

• Tests added
• CHANGELOG entry added

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Overview of commits

• 425c933 - f064a09 - f214f25 - 0b98911 - 7409a55