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/util/ReflectionHelpers.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2021 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.util;
+
+import java.lang.reflect.Field;
+
+public class ReflectionHelpers {
+
+    /**
+     * Reflectively get the value of a field.
+     *
+     * @param object Target object.
+     * @param fieldName The field name.
+     * @param <R> The return type.
+     * @return Value of the field on the object.
+     */
+    public static <R> R getField(Object object, String fieldName) {
+        try {
+            Field field = object.getClass().getDeclaredField(fieldName);
+            field.setAccessible(true);
+            return (R) field.get(object);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Reflectively set the value of a field.
+     *
+     * @param object Target object.
+     * @param fieldName The field name.
+     * @param fieldNewValue New value.
+     */
+    public static void setField(Object object, String fieldName, Object fieldNewValue) {
+        try {
+            Field field = object.getClass().getDeclaredField(fieldName);
+            field.setAccessible(true);
+            field.set(object, fieldNewValue);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+}