* add multinomial probability distribution
* fix categorical sample bug when logits less than zero
* fix categorical sample can't pass hypothesis test and entropy shape error bug

* add beta distribution
* add kl_divergence and register_kl api

* extend Distribution baseclass for supporting multivariant distribution and prob method

* add ExponentialFamily base class and entropy using Bregman divergence

* add dirichlet probability distribution

* add dirichlet sample op and cpu backend kernel

* add Dirichlet op cuda kernel  (#6)

* add dirichlet op hip kernel
Co-authored-by: NFeiyu Chan <chenfeiyu@baidu.com>

move distribution.py into distribution package and split into different file for better scalability (#38047)