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/vision/events/tcp_server.cc b/aos/vision/events/tcp_server.cc
index cf4dd7f..fa2a369 100644
--- a/aos/vision/events/tcp_server.cc
+++ b/aos/vision/events/tcp_server.cc
@@ -16,8 +16,7 @@
 
 #include "aos/logging/logging.h"
 
-namespace aos {
-namespace events {
+namespace aos::events {
 
 namespace {
 
@@ -108,5 +107,4 @@
   loop()->Add(Construct(infd));
 }
 
-}  // namespace events
-}  // namespace aos
+}  // namespace aos::events