Add tools/gen_all

Add a script to invoke all the other code generation scripts, namely:
-  fix_include_guards
-  gen_android_bp
-  gen_merged_protos
-  gen_tracing_cpp_headers_from_protos
-  gen_binary_descriptors

Also remove the .py from gen_tracing_cpp_headers_from_protos.py, to
match all the other scripts.

Change-Id: Ibc71110152879ef460363ca02144146c8d83d01e
diff --git a/src/tracing/core/test_config.cc b/src/tracing/core/test_config.cc
index 270be69..8797261 100644
--- a/src/tracing/core/test_config.cc
+++ b/src/tracing/core/test_config.cc
@@ -22,7 +22,7 @@
  * by
  * ../../tools/proto_to_cpp/proto_to_cpp.cc.
  * If you need to make changes here, change the .proto file and then run
- * ./tools/gen_tracing_cpp_headers_from_protos.py
+ * ./tools/gen_tracing_cpp_headers_from_protos
  */
 
 #include "perfetto/tracing/core/test_config.h"