Expose LocationManager#getNetworkProviderPackage as @SystemApi

The PermissonController is going to become a mainline module, hence it
has to compile against @SystemApi.

The permission controller needs to know which package is the network
provider as it treats the location permission of the location provider
page special.

As far as I understood the current API is not protected. I would like to
leave adding the protection to the location team.

Bug: 110953302
Test: Built
Change-Id: Ic0691bd2254137273160ee6c2e6bb10257205d54

location/java/android/location/LocationManager.java

@@ -2378,4 +2378,17 @@ public class LocationManager {
             throw new IllegalArgumentException("invalid geofence: " + fence);
         }
     }
+
+    /**
+     * @hide
+     */
+    @SystemApi
+    public String getNetworkProviderPackage() {
+        try {
+            return mService.getNetworkProviderPackage();
+        } catch (RemoteException e) {
+            e.rethrowFromSystemServer();
+            return null;
+        }
+    }
 }