TCP socket monitoring: minimum SockDiag primitives

This patch adds a getSocketsInfo() method on the SockDiag class for
dumping the struct tcp_info of all IPv4 and IPv6 sockets on the system,
using the sock_diag netlink interface.

Bug: 64147860
Test: - manual tests usint dumpsys command from follow-up patch
      - TODO: netd unit tests
Change-Id: I3ad1726b4fde005c7b9506af96ed7bd79f527316
2 files changed