Extend netlink class to fit the data structure

In order to get the tcp_info via netlink socket from kernel,
NetworkStack needs to use netlink class to pack and parse the
InetDiagReq. Current design hardcodes ididag_ext field in
InetDiagReqV2. The structure is also not allowed to take null
id to not to specify certain socket. Update the constructor and
backward support exising constructor.

Bug: 136162280
Test: atest FrameworksNetTests NetworkStackTests
Change-Id: Id66da1797da183ae3d99073f80bad1df929946dc