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/gen_tracing_cpp_headers_from_protos b/tools/gen_tracing_cpp_headers_from_protos
index 44187a7..e02c539 100755
--- a/tools/gen_tracing_cpp_headers_from_protos
+++ b/tools/gen_tracing_cpp_headers_from_protos
@@ -17,7 +17,7 @@
 import subprocess
 import sys
 
-CORE_H = 'include/perfetto/tracing/core'
+CORE_H = 'include/perfetto/ext/tracing/core'
 CORE_CPP = 'src/tracing/core'
 
 PROTOS = (
@@ -40,9 +40,9 @@
 )
 
 
-HEADER_PATH = 'include/perfetto/tracing/core'
+HEADER_PATH = 'include/perfetto/ext/tracing/core'
 CPP_PATH = 'src/tracing/core'
-INCLUDE_PATH = 'perfetto/tracing/core'
+INCLUDE_PATH = 'perfetto/ext/tracing/core'
 ROOT_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))