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/aos/events/timing_statistics_test.cc b/aos/events/timing_statistics_test.cc
index 9a7fefc..a8a45eb 100644
--- a/aos/events/timing_statistics_test.cc
+++ b/aos/events/timing_statistics_test.cc
@@ -4,9 +4,7 @@
 
 #include "aos/flatbuffers.h"
 
-namespace aos {
-namespace internal {
-namespace testing {
+namespace aos::internal::testing {
 
 TEST(TimingStatistic, StatisticsTest) {
   flatbuffers::FlatBufferBuilder fbb;
@@ -67,6 +65,4 @@
   EXPECT_NEAR(statistic.message().standard_deviation(), 5.2372293656638, 1e-6);
 }
 
-}  // namespace testing
-}  // namespace internal
-}  // namespace aos
+}  // namespace aos::internal::testing