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/IntSetTest.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2018 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 static com.google.common.truth.Truth.assertThat;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import androidx.test.filters.SmallTest;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/**
+ * Unit tests for {@link IntSet}
+ */
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public class IntSetTest {
+
+    @Test
+    public void shouldBeEmptyInitially() {
+        IntSet set = new IntSet();
+        assertThat(set.size()).isEqualTo(0);
+    }
+
+    @Test
+    public void oneElementSet() {
+        IntSet set = new IntSet();
+        set.add(2);
+        assertThat(set.size()).isEqualTo(1);
+        assertTrue(set.contains(2));
+        assertFalse(set.contains(1));
+    }
+
+
+    @Test
+    public void twoElementSet() {
+        IntSet set = new IntSet();
+        set.add(2);
+        set.add(1);
+        assertThat(set.size()).isEqualTo(2);
+        assertTrue(set.contains(2));
+        assertTrue(set.contains(1));
+    }
+
+    @Test
+    public void threeElementSet() {
+        IntSet set = new IntSet();
+        set.add(2);
+        set.add(1);
+        set.add(10);
+        assertThat(set.size()).isEqualTo(3);
+        assertEquals("1, 2, 10", set.mArray.toConcatString());
+    }
+
+
+    @Test
+    public void duplicateEntries() {
+        IntSet set = new IntSet();
+        set.add(2);
+        set.add(2);
+        assertEquals(1, set.size());
+    }
+}