Add underpinned Network parameter in SocketKeepalive.start()

Take a Network parameter to have an one-to-one mapping between
keepalive and its underpinned network on the automatic keepalive.

Existing design could not really tell which network should the
automatic keepalive check for the TCP socket status if there are
multiple automatic keepalives enabled, e.g. Bothe IWLAN and VPN
on WiFi enable the automatic keepalive. The keepalive for IWLAN
should check if there are any TCP sockets on the IWLAN network
instead of VPN network.

Bug: 259000745
Test: atest FrameworksNetTests
Test: Cts in the follow up commit
Change-Id: I7353f4ef43e8fdad02c4d4a0bb5f6efa7d94c1b4
7 files changed