GitLab

* added relgraphconv

* add tests for CuGraphRelGraphConv

* move test to tests directory

* update docs

* address PR review 1

* address PR review, continued

* remove stashing ctx.device

* make fanout optional

* fanout -> max_in_degree

* improve docstrings consistency

* initialize parameters directly in __init__

* get rid of shared memory size check

* improve docs

* format comments

* skip test case for regularizer=None
Co-authored-by: Mufei Li <mufeili1996@gmail.com>
Co-authored-by: Hongzhi (Steve), Chen <chenhongzhi.nkcs@gmail.com>