staticd: Add SRv6 encap behavior in show running-config

staticd: Add SRv6 encap behavior in show running-config

This commit extends the output of `show running-config` to display the
configured SRv6 encapsulation behavior.

```
router# show running-config
[...]
ip route 192.0.2.2/32 sr0 segments fcbb:bbbb:1:2:3:4:5:6/fcbb:bbbb:7:8:fe00:: encap-behavior H_Encaps
ip route 192.0.2.3/32 sr0 segments fcbb:bbbb:1:2:3:4:5:6/fcbb:bbbb:7:8:fe00:: encap-behavior H_Encaps_Red
ipv6 route 2001:db8:1:1::2/128 sr0 segments fcbb:bbbb:1:2:3:4:5:6/fcbb:bbbb:7:8:fe00:: encap-behavior H_Encaps
ipv6 route 2001:db8:1:1::3/128 sr0 segments fcbb:bbbb:1:2:3:4:5:6/fcbb:bbbb:7:8:fe00:: encap-behavior H_Encaps_Red
[...]
```

Signed-off-by: Carmine Scarpitta <cscarpit@cisco.com>