[Wi-Fi] Add basic UI structure for adding Wi-Fi for apps feature.

Add following changes:
1. Add intent receiver.
2. Add panel UI with icon, title, summary.
3. Add two buttons (save and cancel).
4. Add test case for activity and fragment

Bug: 136472483
Test: Add following test cases for checking button and package name in activity and fragment.
      1. AddAppNetworksActivityTest
      2. AddAppNetworksFragmentTest
Change-Id: I5515a96fa3feb0e3e6d68159b2c0dec0894c15ee

tests/robotests/src/com/android/settings/wifi/addappnetworks/AddAppNetworksActivityTest.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.wifi.addappnetworks;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.robolectric.Shadows.shadowOf;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.Robolectric;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(RobolectricTestRunner.class)
+public class AddAppNetworksActivityTest {
+
+    @Test
+    public void startActivity_withPackageName_bundleShouldHaveRightPackageName() {
+        final String packageName = RuntimeEnvironment.application.getPackageName();
+        final AddAppNetworksActivity activity =
+                Robolectric.buildActivity(AddAppNetworksActivity.class).create().get();
+        shadowOf(activity).setCallingPackage(packageName);
+
+        activity.showAddNetworksFragment();
+
+        assertThat(activity.mBundle.getString(AddAppNetworksActivity.KEY_CALLING_PACKAGE_NAME))
+                .isEqualTo(packageName);
+    }
+}

tests/robotests/src/com/android/settings/wifi/addappnetworks/AddAppNetworksFragmentTest.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.wifi.addappnetworks;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.spy;
+
+import android.content.Context;
+import android.os.Bundle;
+
+import androidx.fragment.app.FragmentActivity;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.shadows.androidx.fragment.FragmentController;
+
+@RunWith(RobolectricTestRunner.class)
+public class AddAppNetworksFragmentTest {
+    private static final String FAKE_APP_NAME = "fake_app_name";
+    private FragmentActivity mActivity;
+    private AddAppNetworksFragment mAddAppNetworksFragment;
+    private Context mContext;
+
+    @Before
+    public void setUp() {
+        mAddAppNetworksFragment = spy(new AddAppNetworksFragment());
+        MockitoAnnotations.initMocks(this);
+
+        // Set up bundle
+        final Bundle bundle = new Bundle();
+        bundle.putString(AddAppNetworksActivity.KEY_CALLING_PACKAGE_NAME, FAKE_APP_NAME);
+        doReturn(bundle).when(mAddAppNetworksFragment).getArguments();
+
+        FragmentController.setupFragment(mAddAppNetworksFragment);
+    }
+
+    @Test
+    public void callingPackageName_onCreateView_shouldBeCorrect() {
+        assertThat(mAddAppNetworksFragment.mCallingPackageName).isEqualTo(FAKE_APP_NAME);
+    }
+
+    @Test
+    public void launchFragment_shouldShowSaveButton() {
+        assertThat(mAddAppNetworksFragment.mSaveButton).isNotNull();
+    }
+
+    @Test
+    public void launchFragment_shouldShowCancelButton() {
+        assertThat(mAddAppNetworksFragment.mCancelButton).isNotNull();
+    }
+}