Support reevaluation request from captive portal app

CaptivePortalLogin use similar way to validate the network as
NetworkMonitor. Provide API to reuse NetworkMonitor facilities
for consistent captive portal detection.

Bug: 134892996
Test: atest FrameworksNetTests NetworkStackTests NetworkStackNextTests
Test: manually test with captive portal Wi-Fi
Test: make system-api-stubs-docs-update-current-api \
      test-api-stubs-docs-update-current-api
Change-Id: I6f039eae7ceb18eb6c3cf15587cdc27a7fe35b00

tests/net/common/java/android/net/CaptivePortalTest.java

@@ -43,6 +43,11 @@ public class CaptivePortalTest {
             mCode = response;
         }
 
+        @Override
+        public void appRequest(final int request) throws RemoteException {
+            mCode = request;
+        }
+
         @Override
         public void logEvent(int eventId, String packageName) throws RemoteException {
             mCode = eventId;
@@ -79,6 +84,12 @@ public class CaptivePortalTest {
         assertEquals(result.mCode, CaptivePortal.APP_RETURN_WANTED_AS_IS);
     }
 
+    @Test
+    public void testReevaluateNetwork() {
+        final MyCaptivePortalImpl result = runCaptivePortalTest(c -> c.reevaluateNetwork());
+        assertEquals(result.mCode, CaptivePortal.APP_REQUEST_REEVALUATION_REQUIRED);
+    }
+
     @Test
     public void testLogEvent() {
         final MyCaptivePortalImpl result = runCaptivePortalTest(c -> c.logEvent(