Refactor and modernize namespace declarations

Move all unit tests to namespace nfd::tests

Delete unused header core/algorithm.hpp

Change-Id: I5591f0c5f3bb5db67f8b45fae95471f8a555ca68
diff --git a/daemon/face/unicast-udp-transport.hpp b/daemon/face/unicast-udp-transport.hpp
index 991d561..7c96fef 100644
--- a/daemon/face/unicast-udp-transport.hpp
+++ b/daemon/face/unicast-udp-transport.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2020,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -28,8 +28,7 @@
 
 #include "datagram-transport.hpp"
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NFD_LOG_MEMBER_DECL_SPECIALIZED((DatagramTransport<boost::asio::ip::udp, Unicast>));
 
@@ -59,7 +58,6 @@
   scheduler::ScopedEventId m_closeIfIdleEvent;
 };
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face
 
 #endif // NFD_DAEMON_FACE_UNICAST_UDP_TRANSPORT_HPP