Enable C++ dynamic shape guards by default (pytorch#140756)

Pull Request resolved: pytorch#140756
Approved by: https://github.com/anijain2305
ghstack dependencies: pytorch#149149, pytorch#149197, pytorch#149211

Author: isuruf

torch/_dynamo/config.py

@@ -396,7 +396,7 @@
 enable_cpp_guard_manager = True
 
 # Use C++ guard manger for symbolic shapes
-enable_cpp_symbolic_shape_guards = False
+enable_cpp_symbolic_shape_guards = not is_fbcode()
 
 # Enable tracing through contextlib.contextmanager
 enable_trace_contextlib = True