Volume: Add AIDL placeholder implementation and vts test

Bug: 258124419
Test: atest VtsHalVolumeTargetTest

Change-Id: Ie3eaa820f94be0287ba72b7647d3d7ab8b5c70b8
diff --git a/audio/aidl/TEST_MAPPING b/audio/aidl/TEST_MAPPING
index bf86d01..5ecf9e7 100644
--- a/audio/aidl/TEST_MAPPING
+++ b/audio/aidl/TEST_MAPPING
@@ -31,6 +31,9 @@
       "name": "VtsHalVisualizerTargetTest"
     },
     {
+      "name": "VtsHalVolumeTargetTest"
+    },
+    {
       "name": "VtsHalAECTargetTest"
     },
     {