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
diff --git a/tests/Android.bp b/tests/Android.bp
index aadf99e..8945a1c 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -54,6 +54,7 @@
         "liblzma",
         "libnativehelper",
         "libnetworkstacktestsjni",
+        "libnetworkstackutilsjni",
         "libpackagelistparser",
         "libpcre2",
         "libprocessgroup",