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/src/tracing/core/tracing_service_impl.h b/src/tracing/core/tracing_service_impl.h
index fba189d..3d734cd 100644
--- a/src/tracing/core/tracing_service_impl.h
+++ b/src/tracing/core/tracing_service_impl.h
@@ -25,17 +25,17 @@
 #include <vector>
 
 #include "perfetto/base/logging.h"
-#include "perfetto/base/optional.h"
-#include "perfetto/base/time.h"
-#include "perfetto/base/weak_ptr.h"
-#include "perfetto/tracing/core/basic_types.h"
-#include "perfetto/tracing/core/commit_data_request.h"
-#include "perfetto/tracing/core/data_source_descriptor.h"
-#include "perfetto/tracing/core/observable_events.h"
-#include "perfetto/tracing/core/shared_memory_abi.h"
-#include "perfetto/tracing/core/trace_config.h"
-#include "perfetto/tracing/core/trace_stats.h"
-#include "perfetto/tracing/core/tracing_service.h"
+#include "perfetto/ext/base/optional.h"
+#include "perfetto/ext/base/time.h"
+#include "perfetto/ext/base/weak_ptr.h"
+#include "perfetto/ext/tracing/core/basic_types.h"
+#include "perfetto/ext/tracing/core/commit_data_request.h"
+#include "perfetto/ext/tracing/core/data_source_descriptor.h"
+#include "perfetto/ext/tracing/core/observable_events.h"
+#include "perfetto/ext/tracing/core/shared_memory_abi.h"
+#include "perfetto/ext/tracing/core/trace_config.h"
+#include "perfetto/ext/tracing/core/trace_stats.h"
+#include "perfetto/ext/tracing/core/tracing_service.h"
 #include "src/tracing/core/id_allocator.h"
 
 namespace perfetto {