Add VCN CTS and unit tests to presubmit for VCN changes

Verified that VCN CTS and unit tests are runnning in presubmit:
https://android-build.corp.google.com/test_investigate/?invocationId=I96600010143119977&testResultId=TR64528561645495936

Bug: 274822877
Test: no function code change
Change-Id: Ic3beb9f5966663de386d1aa49d9b06ab227eb5f4

services/core/java/com/android/server/vcn/TEST_MAPPING

@@ -0,0 +1,10 @@
+{
+  "presubmit": [
+    {
+      "name": "FrameworksVcnTests"
+    },
+    {
+      "name": "CtsVcnTestCases"
+    }
+  ]
+}