Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/frc971/codelab/basic_test.cc b/frc971/codelab/basic_test.cc
index e9820bc..b2ad83e 100644
--- a/frc971/codelab/basic_test.cc
+++ b/frc971/codelab/basic_test.cc
@@ -18,9 +18,7 @@
 #include "frc971/control_loops/control_loop_test.h"
 #include "frc971/control_loops/team_number_test_environment.h"
 
-namespace frc971 {
-namespace codelab {
-namespace testing {
+namespace frc971::codelab::testing {
 
 namespace chrono = ::std::chrono;
 using aos::monotonic_clock;
@@ -238,6 +236,4 @@
   basic_simulation_.VerifyResults(0.0, false);
 }
 
-}  // namespace testing
-}  // namespace codelab
-}  // namespace frc971
+}  // namespace frc971::codelab::testing