Rename KeysetUtil to TestKeysetHandle and make it testonly = 1.

PiperOrigin-RevId: 238715069
GitOrigin-RevId: 91e305090a18bd579c842459a6f46de1f2861763
diff --git a/cc/cleartext_keyset_handle.h b/cc/cleartext_keyset_handle.h
index 51c248c..9a74039 100644
--- a/cc/cleartext_keyset_handle.h
+++ b/cc/cleartext_keyset_handle.h
@@ -36,6 +36,10 @@
   static crypto::tink::util::StatusOr<std::unique_ptr<KeysetHandle>> Read(
       std::unique_ptr<KeysetReader> reader);
 
+  // Creates a KeysetHandle object for the given 'keyset'.
+  static std::unique_ptr<KeysetHandle> GetKeysetHandle(
+      const google::crypto::tink::Keyset& keyset);
+
   // Returns a Keyset-proto from the given 'keyset_handle'.
   static const google::crypto::tink::Keyset& GetKeyset(
       const KeysetHandle& keyset_handle);