Merge "[KA04] Expose TCP socket keepalive API"

api/system-current.txt

core/java/android/net/ConnectivityManager.java

core/java/android/net/IConnectivityManager.aidl

core/java/android/net/NetworkAgent.java

core/java/android/net/SocketKeepalive.java

core/java/android/net/TcpSocketKeepalive.java

core/java/android/net/ip/IIpClient.aidl

packages/NetworkStack/src/android/net/apf/ApfFilter.java

packages/NetworkStack/src/android/net/ip/IpClient.java

packages/NetworkStack/tests/Android.bp

...ces/core/java/com/android/server/ConnectivityService.java

...ava/com/android/server/connectivity/KeepaliveTracker.java

...m/android/server/connectivity/TcpKeepaliveController.java