[add] benchmark scripts

Context

This MR is part of aidge_core#262 to add a benchmark system.

Major modifications

• add: benchmark.py with functions to run a GraphView and return its execution time and output in the wider context of benchmark.

aidge_export_cpp/__init__.py

@@ -7,4 +7,4 @@ from .export_registry import ExportLibCpp
 from .operators import *
 from collections import defaultdict
 from .export import *
-
+from . import benchmark