Add a basic test case to the new instrumentation test

However, due to the hard limit (60s) on the timeout during the
presubmit, the test is registered as a postsubmit test for now.

Also implement some helper methods and classes to make writing tests
easy.

Bug: 203483081
Test: atest MicrodroidTestApp
Change-Id: Ic07d776aff5f56421fc43a103a5b54b4a62b451f
diff --git a/TEST_MAPPING b/TEST_MAPPING
index b805d03..69f5518 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -10,6 +10,11 @@
       "name": "VirtualizationTestCases"
     }
   ],
+  "postsubmit": [
+    {
+      "name": "MicrodroidTestApp"
+    }
+  ],
   "imports": [
     {
       "path": "packages/modules/Virtualization/apkdmverity"