Add test api for setting vendor disk image

So far only a single test asserting that setting vendor disk image
requires caller to have USE_CUSTOM_VIRTUAL_MACHINE permission. More
tests to come in the follow up changes.

Bug: 285855433
Test: atest MicrodroidTestApp
Change-Id: Ic68fccbb8f916f30cab1d772f45714d1e75369a2
diff --git a/tests/testapk/AndroidManifest.xml b/tests/testapk/AndroidManifest.xml
index 2ea3f6c..d6e6004 100644
--- a/tests/testapk/AndroidManifest.xml
+++ b/tests/testapk/AndroidManifest.xml
@@ -22,8 +22,7 @@
     <queries>
         <package android:name="com.android.microdroid.vmshare_app" />
     </queries>
-    <application>
-    </application>
+    <application />
     <instrumentation android:name="androidx.test.runner.AndroidJUnitRunner"
         android:targetPackage="com.android.microdroid.test"
         android:label="Microdroid Test" />