wallet: Do not include server symbols

ui_interface is in libbitcoin_server and can not be included in the
wallet because the wallet does not link with server symbols.

src/util/ui_change_type.h

@@ -0,0 +1,15 @@
+// Copyright (c) 2012-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_UI_CHANGE_TYPE_H
+#define BITCOIN_UTIL_UI_CHANGE_TYPE_H
+
+/** General change type (added, updated, removed). */
+enum ChangeType {
+    CT_NEW,
+    CT_UPDATED,
+    CT_DELETED
+};
+
+#endif // BITCOIN_UTIL_UI_CHANGE_TYPE_H