* Move GumbelSoftmax OP to phi

* platform::errors -> phi::errors; GumbelSoftmaxGradInferMeta -> backend.h/cc

* Use axis util in kernel impl

* Remove namespace platform::errors

* Use GetCPUEngine in Device Context

* Add New Op: gumbel_softmax

* Add New Op: gumbel_softmax

* Add New Op: gumbel_softmax (amend)

* add __main__ function in unit test

* fix bugs when test in windows ci

* update en docs

* delete reletive error in unit test

* delete relative error in unit test

* set hard=True in unit test