Move attach*Filter() and addArpEntry() methods to NetworkStack

The SocketUtils.attach*Filter and SocketUtils.addArpEntry methods
were added there because they could not be added as JNI inside
the NetworkStack. This was not possible because on Go devices,
the NetworkStack was a jar library. But now, Go also uses an APK.
Hence, move these methods to the NetworkStack.

Change-Id: I1d88a0f0be23f2b15d5103fa092b9bf982329d7c
Fix: 129433183
Test: atest NetworkStackTests FrameworksNetTests