bgpd: Adopt `show bgp detail-routes` command for L3VPN outputs as well

bgpd: Adopt `show bgp detail-routes` command for L3VPN outputs as well

```
unet> sh pe2 vtysh -c 'sh ip bgp ipv4 vpn detail-routes'
BGP table version is 4, local router ID is 10.10.10.20, vrf id 0
Default local pref 100, local AS 65001
Route Distinguisher: 192.168.2.2:2
BGP routing table entry for 192.168.2.2:2:10.0.0.0/24, version 1
not allocated
Paths: (1 available, best #1)
  Not advertised to any peer
  65000
    192.168.2.1 from 0.0.0.0 (10.10.10.20) vrf RED(4) announce-nh-self
      Origin incomplete, metric 0, localpref 50, valid, sourced, local, best (First path received)
      Extended Community: RT:192.168.2.2:2
      Originator: 10.10.10.20
      Remote label: 2222
      Last update: Tue Dec 20 13:01:20 2022
BGP routing table entry for 192.168.2.2:2:172.16.255.1/32, version 2
not allocated
Paths: (1 available, best #1)
  Not advertised to any peer
  65000
    192.168.2.1 from 0.0.0.0 (10.10.10.20) vrf RED(4) announce-nh-self
      Origin incomplete, localpref 50, valid, sourced, local, best (First path received)
      Extended Community: RT:192.168.2.2:2
      Originator: 10.10.10.20
      Remote label: 2222
      Last update: Tue Dec 20 13:01:20 2022
BGP routing table entry for 192.168.2.2:2:192.168.1.0/24, version 3
not allocated
Paths: (1 available, best #1)
  Not advertised to any peer
  65000
    192.168.2.1 from 0.0.0.0 (10.10.10.20) vrf RED(4) announce-nh-self
      Origin incomplete, localpref 50, valid, sourced, local, best (First path received)
      Extended Community: RT:192.168.2.2:2
      Originator: 10.10.10.20
      Remote label: 2222
      Last update: Tue Dec 20 13:01:20 2022
BGP routing table entry for 192.168.2.2:2:192.168.2.0/24, version 4
not allocated
Paths: (1 available, best #1)
  Not advertised to any peer
  65000
    192.168.2.1 from 0.0.0.0 (10.10.10.20) vrf RED(4) announce-nh-self
      Origin incomplete, metric 0, localpref 50, valid, sourced, local, best (First path received)
      Extended Community: RT:192.168.2.2:2
      Originator: 10.10.10.20
      Remote label: 2222
      Last update: Tue Dec 20 13:01:20 2022

Displayed  4 routes and 4 total paths
```

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>