Change Tethering package name

".apex" is easy to confuse.
Rename as below:
apex: com.android.tethering.apex -> com.android.tethering
apk: com.android.tethering -> com.android.networkstack.tethering

Bug: 146471733
Test: build

Change-Id: I2c7647abb996539a3af6cfe0e0214a5e8927c0d6
diff --git a/Tethering/AndroidManifestBase.xml b/Tethering/AndroidManifestBase.xml
index dc013da..fa85f66 100644
--- a/Tethering/AndroidManifestBase.xml
+++ b/Tethering/AndroidManifestBase.xml
@@ -17,7 +17,7 @@
  */
 -->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-          package="com.android.tethering"
+          package="com.android.networkstack.tethering"
           android:versionCode="1"
           android:versionName="R-initial">
     <application