Refactor(eos_designs): Rebuild the models for route-targets under VRF and Vlans

[gmuloc]

Draft model

Warning

@gmuloc this is what made sense in 4.35 at the time of opening this issue
please double check before implementing
for non evpn AF we could argue having route_targets as a list

route_target:
  evpn:
    import:
      route_targets: # no primary key
        - route_target: <route_target>
           domain: <str, remote, all> # none means local
      route_map: <str>
      rcf: 
         function: <function>
    export:
      route_targets: # no primary key
        - route_target: <route_target>
           domain: <str, remote, all> # none means local
      route_map: <str>
      rcf: 
         function: <function>
      imported_route: bool
  vpn_ipv4:
    import:
      route_targets: 
        - route_target: <route_target>
      route_map: <str>
      rcf: 
         function: <function>
        vrf_route_filter_rcf: <function>
    export:
      route_targets: 
        - route_target: <route_target>
      route_map: <str>
      rcf: 
         function: <function>
        vrf_route_filter_rcf: <function>
      label:
        allocation_nexthop_default_route: <bool>
      imported_route: bool
  vpn_ipv6:
    import:
      route_targets: 
        - route_target: <route_target>
      route_map: <str>
      rcf: 
         function: <function>
        vrf_route_filter_rcf: <function>
    export:
      route_targets: 
        - route_target: <route_target>
      route_map: <str>
      rcf: 
         function: <function>
        vrf_route_filter_rcf: <function>
      label:
        allocation_nexthop_default_route: <bool>
      imported_route: bool
  flow-spec-vpn-ipv4:
    import:
      route_targets: 
        - route_target: <route_target>
    export:
      route_targets: 
        - route_target: <route_target>
  flow-spec-vpn-ipv6:
    import:
      route_targets: 
        - route_target: <route_target>
    export:
      route_targets: 
        - route_target: <route_target>

Originally posted by @gmuloc in #6529 (comment)