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.cpp b/daemon/face/network-predicate.cpp
index 07de63c..a13d886 100644
--- a/daemon/face/network-predicate.cpp
+++ b/daemon/face/network-predicate.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,
@@ -29,8 +29,7 @@
 
 #include <fnmatch.h>
 
-namespace nfd {
-namespace face {
+namespace nfd::face {
 
 NetworkPredicateBase::NetworkPredicateBase()
 {
@@ -227,5 +226,4 @@
                       [&address] (const auto& rule) { return doesAddressMatchRule(address, rule); });
 }
 
-} // namespace face
-} // namespace nfd
+} // namespace nfd::face