staticd: Extend CLI to support encap behavior

staticd: Extend CLI to support encap behavior

This commit extends the staticd CLI to allow users to specify the SRv6
encapsulation behavior when creating an ip/ipv6 route.

```
router(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
router(config)# 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
router(config)# 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
router(config)# 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>