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/network-predicate.hpp b/daemon/face/network-predicate.hpp
index 7f77486..2ea79d6 100644
--- a/daemon/face/network-predicate.hpp
+++ b/daemon/face/network-predicate.hpp
@@ -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,
@@ -30,8 +30,7 @@
 
 #include <ndn-cxx/net/network-interface.hpp>
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 class NetworkPredicateBase
 {
@@ -130,7 +129,6 @@
   isRuleValid(const std::string& key, const std::string& value) final;
 };
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face
 
 #endif // NFD_DAEMON_FACE_NETWORK_PREDICATE_HPP