Add netlink attributes field into the InetDiagMessage

Add nlAttrs parameter to store the remaining attributes data.

As a part of follow-up work from aosp/2354202, the TCP socket
parsing can be done by using existing InetDiagMessage class.
The missing piece in the InetDiagMessage class is the possible
netlink attributes fields that may be appended after an
InetDiagMessage.

Bug: 311119352
Bug: 265877161
Test: atest NetworkStaticLibTests
Change-Id: I9c34166124fd4efba2ab211bfb537ccce5e774a4