Make TetheringManager to system API

Also deprecated tethering APIs in ConnectivityManager.
Will have follow up change to remove @hide tethering function in
ConnectivityManager.

Bug: 145093446
Bug: 148038547
Test: -build, flash, boot
      -atest TetheringTests

Change-Id: Ia432057bf9056727c4a0ca97d160a49274d33581
Merged-In: Ia432057bf9056727c4a0ca97d160a49274d33581
diff --git a/Android.bp b/Android.bp
index f57acfa..6874b6e 100644
--- a/Android.bp
+++ b/Android.bp
@@ -646,7 +646,10 @@
     name: "framework-tethering-annotations",
     srcs: [
         "core/java/android/annotation/NonNull.java",
+        "core/java/android/annotation/Nullable.java",
+        "core/java/android/annotation/RequiresPermission.java",
         "core/java/android/annotation/SystemApi.java",
+        "core/java/android/annotation/TestApi.java",
     ],
 }
 // Build ext.jar