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/tools/nfdc/status-report.t.cpp b/tests/tools/nfdc/status-report.t.cpp
index 2ab5c3e..f978c57 100644
--- a/tests/tools/nfdc/status-report.t.cpp
+++ b/tests/tools/nfdc/status-report.t.cpp
@@ -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,
@@ -27,10 +27,7 @@
 
 #include "status-fixture.hpp"
 
-namespace nfd {
-namespace tools {
-namespace nfdc {
-namespace tests {
+namespace nfd::tools::nfdc::tests {
 
 const std::string STATUS_XML = stripXmlSpaces(R"XML(
   <?xml version="1.0"?>
@@ -120,7 +117,7 @@
   std::function<void()> processEventsFunc;
 };
 
-class StatusReportModulesFixture : public IoFixture, public KeyChainFixture
+class StatusReportModulesFixture : public nfd::tests::IoFixture, public nfd::tests::KeyChainFixture
 {
 protected:
   StatusReportModulesFixture()
@@ -211,7 +208,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestStatusReport
 BOOST_AUTO_TEST_SUITE_END() // Nfdc
 
-} // namespace tests
-} // namespace nfdc
-} // namespace tools
-} // namespace nfd
+} // namespace nfd::tools::nfdc::tests