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/fw/topology-tester.cpp b/tests/daemon/fw/topology-tester.cpp
index c44d61d..a758ee2 100644
--- a/tests/daemon/fw/topology-tester.cpp
+++ b/tests/daemon/fw/topology-tester.cpp
@@ -30,9 +30,7 @@
 
 #include <ndn-cxx/encoding/encoding-buffer-fwd.hpp>
 
-namespace nfd {
-namespace fw {
-namespace tests {
+namespace nfd::tests {
 
 using face::GenericLinkService;
 using face::InternalClientTransport;
@@ -324,6 +322,4 @@
   }
 }
 
-} // namespace tests
-} // namespace fw
-} // namespace nfd
+} // namespace nfd::tests