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/tests/daemon/face/udp-channel.t.cpp b/tests/daemon/face/udp-channel.t.cpp
index b61e5af..d36e2f5 100644
--- a/tests/daemon/face/udp-channel.t.cpp
+++ b/tests/daemon/face/udp-channel.t.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2021,  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,
@@ -26,11 +26,10 @@
 #include "udp-channel-fixture.hpp"
 
 #include "test-ip.hpp"
+
 #include <boost/mpl/vector.hpp>
 
-namespace nfd {
-namespace face {
-namespace tests {
+namespace nfd::tests {
 
 BOOST_AUTO_TEST_SUITE(Face)
 BOOST_FIXTURE_TEST_SUITE(TestUdpChannel, UdpChannelFixture)
@@ -64,6 +63,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestUdpChannel
 BOOST_AUTO_TEST_SUITE_END() // Face
 
-} // namespace tests
-} // namespace face
-} // namespace nfd
+} // namespace nfd::tests