Visualizer: Add AIDL placeholder implementation and vts test cases

Bug: 258124419
Test: atest VtsHalVisualizerTargetTest

Change-Id: I8bfdb234d1ac3f57b12096d3f02dd1bad92b1d0f
diff --git a/audio/aidl/TEST_MAPPING b/audio/aidl/TEST_MAPPING
index 484320f..b4607f9 100644
--- a/audio/aidl/TEST_MAPPING
+++ b/audio/aidl/TEST_MAPPING
@@ -14,6 +14,9 @@
     },
     {
       "name": "VtsHalLoudnessEnhancerTargetTest"
+    },
+    {
+      "name": "VtsHalVisualizerTargetTest"
     }
   ]
 }