Reshuffle include/ directory layout

This CL reorganizes the include/ directory as follows:
1. The immediate subdirectories of include/ are now the stable API
   surface exposed to all embedders, with the exception of ext/.
2. ext/ contains the unstable API surface that is exposed only to chrome.

Test: builds on all configurations and passes tests
Bug: 132678367
Change-Id: If638d4b4c150fd591cd1db851283b25ff6083ed6
diff --git a/tools/ftrace_proto_gen/proto_gen_utils.cc b/tools/ftrace_proto_gen/proto_gen_utils.cc
index 9e9f34e..79f0ea8 100644
--- a/tools/ftrace_proto_gen/proto_gen_utils.cc
+++ b/tools/ftrace_proto_gen/proto_gen_utils.cc
@@ -23,11 +23,11 @@
 #include <fstream>
 #include <regex>
 
-#include "perfetto/base/file_utils.h"
 #include "perfetto/base/logging.h"
-#include "perfetto/base/pipe.h"
-#include "perfetto/base/string_splitter.h"
-#include "perfetto/base/string_utils.h"
+#include "perfetto/ext/base/file_utils.h"
+#include "perfetto/ext/base/pipe.h"
+#include "perfetto/ext/base/string_splitter.h"
+#include "perfetto/ext/base/string_utils.h"
 
 namespace perfetto {