IS-IS replay tool IPv6 support

I added the IPv6 support to the sniffing tool. The IPv6 messages appear inside the HELLO messages.
In the example below, both IPv4 and IPv6 protocols are supported and parsed:

L1LANHello (len=1500):
    src mac: 00.0c.29.f4.67.aa, dst mac: 01.80.c2.00.00.14
    len: 1500, LLC: 0xfe.fe.03
    hdr_len: 27, protocol id: 1, version: 1, eco: 0, user eco: 0
    circuit type: L1Circuit, holdtimer: 50, PDU len: 1497, priority: 64
    src id: 11.11.11.11.11.11, LAN id: 11.11.11.11.11.11.01
    field: AreaAddress, length: 4
        area addresses: 0x49.00.01,
    field: IIHIISNeighbor, length: 6
        IS Neighbour 1: 00.0c.29.47.e4.a1
    field: ProtoSupported, length: 2
        protocols supported: ['IP', 'IPV6']
    field: IPIfAddr, length: 4
        interface IP addresses: ['192.168.9.131']
    field: IPv6IfAddr, length: 16
        interface IPv6 addresses: ['fe.80.00.00.00.00.00.00.02.0c.29.ff.fe.f4.67.aa']
message len is 1514