Rename device test helper package to com.android.microdroid.test.device

This CL renames the device test helper com.android.microdroid.test to
com.android.microdroid.test.device package to eventually have two
separate separate packages for the device test helper and host
test helper.

Test: atest MicrodroidBenchmarks
Change-Id: I748f8ccda2c94d819ce6f2d75745372db807b693
diff --git a/tests/helper/Android.bp b/tests/helper/Android.bp
index 6d769e6..f77dae5 100644
--- a/tests/helper/Android.bp
+++ b/tests/helper/Android.bp
@@ -16,7 +16,7 @@
 
 java_library_static {
     name: "MicrodroidDeviceTestHelper",
-    srcs: ["src/java/com/android/microdroid/test/*.java"],
+    srcs: ["src/java/com/android/microdroid/test/device/*.java"],
     static_libs: [
         "androidx.test.runner",
         "androidx.test.ext.junit",