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/starter/starter_test.cc b/aos/starter/starter_test.cc
index e68cf05..d26f414 100644
--- a/aos/starter/starter_test.cc
+++ b/aos/starter/starter_test.cc
@@ -17,8 +17,7 @@
 
 using aos::testing::ArtifactPath;
 
-namespace aos {
-namespace starter {
+namespace aos::starter {
 
 class ThreadedStarterRunner {
  public:
@@ -572,5 +571,4 @@
   ASSERT_FALSE(starter.event_loop()->is_running());
 }
 
-}  // namespace starter
-}  // namespace aos
+}  // namespace aos::starter