Access Node Meta and Attrs in template

[dadgar]

This PR allows accessing the Node's attributes and metadata as in a
template.

template {
    data = "{{ env \"attr.unique.network.ip-address\" }}"
    destination = "local/out"
}

[schmichael]

EnvMapAll

[schmichael]

Don't forget a changelog entry

[nugend]

Could a docs clarification around meta be made? It's a little unclear at the moment when something is a node meta value vs a runtime meta value.

[cynicaljoy]

leaving a comment here in hopes it helps somebody...had a case where I wanted to conditionally declare an environment variable if a meta key was a specific value, here's my solution:

      template {
        env = true
        destination = "local/dynamic.env"
        data = <<EOF
{{ $val := env "meta.sometimes_exists_sometimes_doesnt" }}
{{ if eq $val "magic-value" }}HELLO_WORLD=true{{ end }}
EOF
      }

[github-actions]

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