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/util/phased_loop_test.cc b/aos/util/phased_loop_test.cc
index cfe0107..af33567 100644
--- a/aos/util/phased_loop_test.cc
+++ b/aos/util/phased_loop_test.cc
@@ -5,9 +5,7 @@
 
 #include "aos/time/time.h"
 
-namespace aos {
-namespace time {
-namespace testing {
+namespace aos::time::testing {
 
 using ::std::chrono::milliseconds;
 using ::std::chrono::nanoseconds;
@@ -304,6 +302,4 @@
   EXPECT_EQ(4, loop.Iterate((last_time - kOffset) + (kInterval * 4)));
 }
 
-}  // namespace testing
-}  // namespace time
-}  // namespace aos
+}  // namespace aos::time::testing