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/tools/jpeg_vision_test.cc b/aos/vision/tools/jpeg_vision_test.cc
index ef2ec6d..553419a 100644
--- a/aos/vision/tools/jpeg_vision_test.cc
+++ b/aos/vision/tools/jpeg_vision_test.cc
@@ -25,8 +25,7 @@
 #include "aos/vision/image/reader.h"
 #include "aos/vision/math/vector.h"
 
-namespace aos {
-namespace vision {
+namespace aos::vision {
 
 void DrawVLine(ImagePtr ptr, int x, PixelRef color = {255, 0, 0}) {
   for (int y = 0; y < ptr.fmt().h; ++y) {
@@ -108,8 +107,7 @@
   int dx = 0;
   int dy = 0;
 };
-}  // namespace vision
-}  // namespace aos
+}  // namespace aos::vision
 
 int main(int argc, char *argv[]) {
   ::aos::logging::Init();