Generate underlay-ebgp.yaml out of topology file

[dgarros]

Thanks a lot @mpergament, I'll review it ASAP and provide some comments

I like the idea of the role and I have some ideas to make it even simpler

[dgarros]

Hi @mpergament

I propose the following changes

• Remove community from variable file generated by role generate-underlay-ebgp, this parameter is optional and can be different per pod
• Change name of file generated by role generate-underlay-ebgp to indicate that it's a generated file
• Add an unique ID per device in inventory file and use it to generate unique loopback and ASN for each device
• Add a parameter type in topology file to indicate for which link we should generate underlay info, remove the need to name other peer "access"
• Change linkID to ID in both generate-p2p-ips role and in generate-underlay-role

I already implemented these changes but if you have any concerns/suggestions we can always change it back