Self-contained lab topologies

[jbemmel]

https://github.com/ipspace/netlab/blob/2c10748b6b73519ca8fd2b77a90b15e61d1f4e3a/tests/integration/gateway/02-vrrp.yml#L46

It would be useful to have lab topologies that are fully self-contained in a single YAML file. Instead of forking off to a template with a couple of lines of config script, these snippets could be embedded within the single lab file

The above could become:

validate:
  r2_eth1_down:
    description: Remove R2 from the VRRP LAN
    nodes: [ r2 ]
    config:
      template:
        variable.ifstate: 'down'
        eos: |
          interface {{ interfaces[0].ifname }}
          {{ 'no ' if ifstate|default('down') == 'up' else '' }}shutdown
        frr: |
         #!/bin/bash
         ip link set {{ interfaces[0].ifname }} {{ ifstate|default('down') }}
    pass: R2 has been disconnected from the VRRP LAN
    stop_on_error: True

[ipspace]

Good idea. Will try to figure out how to make it work both in validation and in generic custom configuration without too much hassle.

[ipspace]

Implemented in #2573 and #2580