* update comp cost

* add dist default op cost

* add dist fill constant batch size like op cost

* add elewise op cost

* add fill_constant_batch_size_like op cost unittest

* add unittest and remove fill_constant_batch_size_like grad op cost

* add to cmakelist

* fix unittest bug

* update base cost

* update unittest of cost model

* add unittest

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* refactor cost model