Make CBOR and COSE CTS utilities reusable

We need these utilities for tools, and they may prove handy for
production code. Move them into system/security and flesh out the
unit tests.

Test: IdCredSupportTests
Change-Id: I18dd909e46aec5e315adb4358dc23088d70fa899
diff --git a/identity/TEST_MAPPING b/identity/TEST_MAPPING
index 87707a8..6444c56 100644
--- a/identity/TEST_MAPPING
+++ b/identity/TEST_MAPPING
@@ -2,6 +2,9 @@
   "presubmit": [
     {
       "name": "CtsIdentityTestCases"
+    },
+    {
+      "name": "identity-credential-util-tests"
     }
   ]
 }