Add support for Inter AS Option B

[David Gonzalez]

Enhancement summary

Just looking to support the following command:

address-family vpn-ipv4
neighbor default encapsulation mpls next-hop-self received-vpnv4-routes

(command also exists for vpnv-ipv6)

TOI:
https://www.arista.com/en/support/toi/eos-4-24-0f/14476-inter-as-option-b

This is required also when doing EVPN internetworking (EVPN to VPNv4), on the Arista device acting as MPLS ASBR.

Which component of AVD is impacted

eos_cli_config_gen

Use case example

please detail your use case

Describe the solution you would like

This is required also when doing EVPN internetworking (EVPN to VPNv4). On the Arista device, acting as MPLS ASBR, we require this command to exchange VPNv4 routes.

Describe alternatives you have considered

No response

Additional context

No response

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