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/bitpacking_test.cc b/aos/util/bitpacking_test.cc
index 087c719..0f534a1 100644
--- a/aos/util/bitpacking_test.cc
+++ b/aos/util/bitpacking_test.cc
@@ -5,8 +5,7 @@
 
 #include "gtest/gtest.h"
 
-namespace aos {
-namespace testing {
+namespace aos::testing {
 
 // Tests MaskOnes with small arguments.
 TEST(MaskOnesTest, Small) {
@@ -384,5 +383,4 @@
   EXPECT_EQ(0.75f, (IntToFloatLinear<2>(-1.0f, 1.0f, 3)));
 }
 
-}  // namespace testing
-}  // namespace aos
+}  // namespace aos::testing