Modify Android test files (#1021)

To get android build for amber to work internally, I need a few changes. I do
not know enough about the junit testing to know if this will mess anyonly else
up.

I'm also not sure who else uses all of this. Let me know if this causes a
problem.

Author: s-perron

android_gradle/app/src/androidTest/AndroidManifest.xml

@@ -5,4 +5,8 @@
             android:name="com.android.graphics.developerdriver.enable"
             android:value="true" />
     </application>
+
+    <instrumentation android:name="androidx.test.runner.AndroidJUnitRunner"
+      android:targetPackage="com.google.amber"
+      android:label="Amber" />
 </manifest>

android_gradle/app/src/androidTest/java/com/google/amber/AmberLauncher.java

@@ -18,16 +18,16 @@
 
 import android.content.Context;
 import android.os.Bundle;
-
 import androidx.test.platform.app.InstrumentationRegistry;
-
-import org.junit.Test;
-
 import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
 
 // Instrumented test used for launching Amber.
+@RunWith(JUnit4.class)
 public class AmberLauncher {
   @Test
   public void LaunchAmber() {

android_gradle/app/src/main/AndroidManifest.xml

@@ -2,6 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.google.amber">
 
+    <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="33"/>
+
     <application
         android:allowBackup="true"
         android:fullBackupOnly="true"