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/src/com/android/launcher3/testcomponent/WidgetConfigActivity.java

@@ -1,44 +0,0 @@
-/*
- * 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.os.Bundle;
-
-/**
- * Simple activity for widget configuration
- */
-public class WidgetConfigActivity extends BaseTestingActivity {
-
-    public static final String SUFFIX_FINISH = "-finish";
-    public static final String EXTRA_CODE = "code";
-
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        addButton("Cancel", "clickCancel");
-        addButton("OK", "clickOK");
-    }
-
-    public void clickCancel() {
-        setResult(RESULT_CANCELED);
-        finish();
-    }
-
-    public void clickOK() {
-        setResult(RESULT_OK);
-        finish();
-    }
-}