* rewrite get free port strategy

* hide the old one

* make launch compatible

* fix ut

* fix log offset

* [CustomDevice] add custom ccl 2/2

* update

* update

* update launch

* add launch test

* launch test for cpu

* bs 1

* update paddle.distributed.launch

* add sample code

* update shell

* fix typo

* fix typo

* update docs

* rm code

* fix doc 2

* fix doc 3

* fix doc 4
Co-authored-by: Nroot <root@sgjur-pod004-1.ipu.graphcore.cn>

* 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

This reverts commit e680d581.

* [IPU] support paddle.distributed.launch with IPUs

* add device_num to env_args_mapping