network: DHCPv6 client add support for prefix delegation hint

network: DHCPv6 client add support for prefix delegation hint

Add support for prefix hint lenth and prefix hint address
```
Frame 43: 177 bytes on wire (1416 bits), 177 bytes captured (1416 bits) on interface 0
Ethernet II, Src: f6:c1:08:4d:45:f1 (f6:c1:08:4d:45:f1), Dst: IPv6mcast_01:00:02 (33:33:00:01:00:02)
Internet Protocol Version 6, Src: fe80::d250:c82:7f6e:28d6, Dst: ff02::1:2
User Datagram Protocol, Src Port: 546, Dst Port: 547
DHCPv6
    Message type: Solicit (1)
    Transaction ID: 0x5c7902
    Rapid Commit
    Identity Association for Non-temporary Address
    Fully Qualified Domain Name
    Identity Association for Prefix Delegation
        Option: Identity Association for Prefix Delegation (25)
        Length: 41
        Value: 1b97b1690000000000000000001a0019ffffffffffffffff…
        IAID: 1b97b169
        T1: 0
        T2: 0
        IA Prefix
            Option: IA Prefix (26)
            Length: 25
            Value: ffffffffffffffff3c000000000000000000000000000000…
            Preferred lifetime: infinity
            Valid lifetime: infinity
            Prefix length: 60
            Prefix address: ::
    Option Request
    Client Identifier
    Elapsed time
```