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/event_loop_param_test.cc b/aos/events/event_loop_param_test.cc
index 5ec494f..58bfd9b 100644
--- a/aos/events/event_loop_param_test.cc
+++ b/aos/events/event_loop_param_test.cc
@@ -15,8 +15,7 @@
 #include "aos/logging/logging.h"
 #include "aos/realtime.h"
 
-namespace aos {
-namespace testing {
+namespace aos::testing {
 namespace {
 namespace chrono = ::std::chrono;
 }  // namespace
@@ -3692,5 +3691,4 @@
   EXPECT_EQ(SendTestMessage(sender1), RawSender::Error::kMessagesSentTooFast);
 }
 
-}  // namespace testing
-}  // namespace aos
+}  // namespace aos::testing