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
diff --git a/framework/src/android/net/IConnectivityManager.aidl b/framework/src/android/net/IConnectivityManager.aidl
index c8f588d..db001f9 100644
--- a/framework/src/android/net/IConnectivityManager.aidl
+++ b/framework/src/android/net/IConnectivityManager.aidl
@@ -188,7 +188,7 @@
 
     void startNattKeepaliveWithFd(in Network network, in ParcelFileDescriptor pfd, int resourceId,
             int intervalSeconds, in ISocketKeepaliveCallback cb, String srcAddr,
-            String dstAddr, boolean automaticOnOffKeepalives);
+            String dstAddr, boolean automaticOnOffKeepalives, in Network underpinnedNetwork);
 
     void startTcpKeepalive(in Network network, in ParcelFileDescriptor pfd, int intervalSeconds,
             in ISocketKeepaliveCallback cb);