Update Policy Listener API naming.

This CL changes the policy listener API to be
VcnNetworkPolicyChangeListener (it was previously
VcnNetworkPolicyListener) per API Council guidance.

This CL also requires permission NETWORK_FACTORY for removing registered
policy listeners.

Bug: 181562364
Test: atest FrameworksVcnTests
Change-Id: I026eaefa62d8f64b9180fc182a7cf0605d83bf97
Merged-In: I026eaefa62d8f64b9180fc182a7cf0605d83bf97
(cherry picked from commit a96ec13821)

tests/vcn/java/com/android/server/VcnManagementServiceTest.java

@@ -593,6 +593,16 @@ public class VcnManagementServiceTest {
         mVcnMgmtSvc.removeVcnUnderlyingNetworkPolicyListener(mMockPolicyListener);
     }
 
+    @Test(expected = SecurityException.class)
+    public void testRemoveVcnUnderlyingNetworkPolicyListenerInvalidPermission() {
+        doThrow(new SecurityException())
+                .when(mMockContext)
+                .enforceCallingOrSelfPermission(
+                        eq(android.Manifest.permission.NETWORK_FACTORY), any());
+
+        mVcnMgmtSvc.removeVcnUnderlyingNetworkPolicyListener(mMockPolicyListener);
+    }
+
     @Test
     public void testRemoveVcnUnderlyingNetworkPolicyListenerNeverRegistered() {
         mVcnMgmtSvc.removeVcnUnderlyingNetworkPolicyListener(mMockPolicyListener);