Shell: Allow retrieval of wifi network credentials

This permission is needed for some wifi CTS tests.

Is the minimally scoped permission that needs to be added?
- Yes, this only allows the retireval of the saved wifi network
credentials on the device.

What options did you explore that did not need this permission?
- Possibly creating a UI to ask for manual entry of network credentials.
But, that would not let us do automated CTS tests (will need to become
CTS verifier tests then).

Bug: 150236894
Test: atest android.net.wifi.cts.WifiNetworkSpecifierTest
Change-Id: I6881003510191f667950be1ab27a5399fe3914b4

data/etc/privapp-permissions-platform.xml

@@ -330,6 +330,7 @@ applications that come with the platform
         <!-- Needed for test only -->
         <permission name="android.permission.READ_PRECISE_PHONE_STATE" />
         <permission name="android.permission.READ_PRIVILEGED_PHONE_STATE"/>
+        <permission name="android.permission.READ_WIFI_CREDENTIAL"/>
         <permission name="android.permission.REAL_GET_TASKS"/>
         <permission name="android.permission.READ_PRIVILEGED_PHONE_STATE"/>
         <permission name="android.permission.REGISTER_CALL_PROVIDER"/>

packages/Shell/AndroidManifest.xml

@@ -269,6 +269,9 @@
     <!-- Permission needed to test mainline permission module rollback -->
     <uses-permission android:name="android.permission.UPGRADE_RUNTIME_PERMISSIONS" />
 
+    <!-- Permission needed to read wifi network credentials for CtsNetTestCases -->
+    <uses-permission android:name="android.permission.READ_WIFI_CREDENTIAL" />
+
     <application android:label="@string/app_label"
                 android:theme="@android:style/Theme.DeviceDefault.DayNight"
                 android:defaultToDeviceProtectedStorage="true"