Replace existing Robolectric test task with functioning one.

This CL does the following:
- Creates a dir for multivalentTests
- Creates symlinks for the dir to keep Android Studio happy
- Moves many files to the multivalentTests dir
- Adjusts gradle and soong build files to use the new dir as part of
their source sets.

Test: ./gradlew :NexusLauncher:testGoogleWithQuickstepDebugUnitTest
Test: atest Launcher3RoboTests
Fix: 316553886
Bug: 316553889
Flag: NA
Change-Id: Iae28fd0c0191b3ecf9bd2950800875950cca2622

tests/multivalentTests/src/com/android/launcher3/testcomponent/AppWidgetNoConfig.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2017 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.launcher3.testcomponent;
+
+import android.appwidget.AppWidgetProvider;
+
+/**
+ * A simple app widget without any configuration screen.
+ */
+public class AppWidgetNoConfig extends AppWidgetProvider {
+
+
+}