Virtualizer: Add AIDL placeholder implementation and vts test

Bug: 258124419
Test: atest VtsHalVirtualizerTargetTest

Change-Id: Id286ca2e7e201c065969fa70dc707d6a3a010c97
diff --git a/audio/aidl/TEST_MAPPING b/audio/aidl/TEST_MAPPING
index b4607f9..67daa50 100644
--- a/audio/aidl/TEST_MAPPING
+++ b/audio/aidl/TEST_MAPPING
@@ -16,6 +16,9 @@
       "name": "VtsHalLoudnessEnhancerTargetTest"
     },
     {
+      "name": "VtsHalVirtualizerTargetTest"
+    },
+    {
       "name": "VtsHalVisualizerTargetTest"
     }
   ]