Remove last NetworkStack usage of hidden APIs

Includes various small changes to stop using hidden APIs

Test: make NetworkStack
Test: flashed, booted, WiFi and tethering working
Bug: 112869080
Change-Id: Id2830795a444f484b377ed6437435a1cd833697a
diff --git a/Android.bp b/Android.bp
index 225f86de..0407c41 100644
--- a/Android.bp
+++ b/Android.bp
@@ -851,6 +851,7 @@
         "core/java/android/annotation/UnsupportedAppUsage.java",
         "core/java/android/net/DhcpResults.java",
         "core/java/android/util/LocalLog.java",
+        "core/java/com/android/internal/annotations/GuardedBy.java",
         "core/java/com/android/internal/annotations/VisibleForTesting.java",
         "core/java/com/android/internal/util/HexDump.java",
         "core/java/com/android/internal/util/IndentingPrintWriter.java",