Feat(eos_designs): Support for IPv6 in underlay with RFC5549

[xaviramon]

Change Summary

PR required to make #1719 work. Underlay supports IPv6 with RFC5549 and transport of IPv4 VTEP addresses

Related Issue(s)

Fixes #

Component(s) name

arista.avd. eos_designs

Proposed changes

Create new peer-groups for IPv6 AFs
Generate AFs as required
Modify PL and RM to support IPv6 addressing

How to test

molecule

Checklist

User Checklist

• N/A

Repository Checklist

• My code has been rebased from devel before I start
• I have read the CONTRIBUTING document.
• My change requires a change to the documentation and documentation have been updated accordingly.
• I have updated molecule CI testing accordingly. (check the box if not applicable)

[ClausHolbechArista]

I think you are doing too many changes to ipv4 things in here. Basically you should just be adding IPv6 AF for the existing underlay protocol. It should not change everything else.
If someone wants to use different peer-group names, they can just set the names on the existing keys.
Also since you are not removing IPv4, the new name with IPv6 is just as wrong as the IPv4 name.
I suggest to simplify this PR, to just add the underlay AF, loopback, PL etc, and then leave the naming as it is. We can add a new - more neutral - underlay_peers and mlag_underlay_peer later (separate PR)

[ClausHolbechArista]

Also the requirement for rfc5549 is not clear to me. It should just work for regular ibgp/ebgp also right? I understand it will not work for OSPF/ISIS as part of this PR, but I think those are already covered by Emil in the MPLS design.

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[onurgashi]

LGTM!