[Thread] add permission THREAD_NETWORK_TESTING for guarding testing APIs or shell commands

For new Thread network APIs or shell command for only testing, a new
signature permission is deversed to protect them (so to distinguish them
from existing system APIs which are designed for privileged apps such as
GMS Core).

Bug: 329368792
Change-Id: I291989eb0e024614568044945726edc07e20b8be
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index bacab0f..00e17f5 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -602,6 +602,8 @@
 
     <!-- Permission required for CTS test - CtsThreadNetworkTestCases -->
     <uses-permission android:name="android.permission.THREAD_NETWORK_PRIVILEGED"/>
+    <!-- Permission required to access Thread network shell commands for testing -->
+    <uses-permission android:name="android.permission.THREAD_NETWORK_TESTING"/>
 
     <!-- Permission required for CTS tests to enable/disable rate limiting toasts. -->
     <uses-permission android:name="android.permission.MANAGE_TOAST_RATE_LIMITING" />