Add test discovery agent skeleton

Change-Id: I3dacac6d3081a815d07e461561dec380ea63782b
b:371603869
Test:build
diff --git a/ci/Android.bp b/ci/Android.bp
index 6d4ac35..0dfbd37 100644
--- a/ci/Android.bp
+++ b/ci/Android.bp
@@ -102,6 +102,7 @@
         "optimized_targets.py",
         "test_mapping_module_retriever.py",
         "build_context.py",
+        "test_discovery_agent.py",
     ],
 }