Add system service for accessing SystemConfig

Add SystemConfigService and associated AIDLs and permissions for
accessing SystemConfig. The service returns values obtained from a
static instance of com.android.server.SystemConfig.

Bug: 143112379
Test: atest SystemConfigTest
Change-Id: I1a863ae9f53db21d698376008e5b1da83309b141
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index 347d6c2..8a809f2 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -218,7 +218,10 @@
     <!-- Permission required for CTS test - UiModeManagerTest -->
     <uses-permission android:name="android.permission.ENTER_CAR_MODE_PRIORITIZED"/>
 
-      <!-- Permission required for CTS test - CarModeInCallServiceTest -->
+    <!-- Permission required for CTS test - SystemConfigTest -->
+    <uses-permission android:name="android.permission.READ_CARRIER_APP_INFO"/>
+
+    <!-- Permission required for CTS test - CarModeInCallServiceTest -->
     <uses-permission android:name="android.permission.CONTROL_INCALL_EXPERIENCE"/>
 
     <!-- Permission requried for CTS test - CellBroadcastIntentsTest -->