Testing function for chunked memory pool test

[LWisteria]

Theare are many same parts for memory pool test. e.g. https://github.com/fixstars/clpy/blob/65143ed545a2f1f7662b713d8a5fd7d8327c53e4/tests/clpy_tests/opencl_tests/test_carray.py#L12-L17

Those causes maintainance risk. Unify them into a function of testing tool.