[KA04] Expose TCP socket keepalive API

The new set of API allows applications to request keepalives
offload for established TCP sockets over wifi.

However, the application must not write to or read from the
socket after calling this method, until specific callbacks are
called.

Bug: 114151147
Test: atest FrameworksNetTests FrameworksWifiTests NetworkStackTests

Change-Id: I3880505dbc35fefa34ef6c79555458ecf5d296a4