Add RNNCell modules to Script standard library (#14695)
Summary:
Adds RNNCell modules to script standard lib
cc apaszke for argument_spec changes
Pull Request resolved: https://github.com/pytorch/pytorch/pull/14695
Differential Revision: D13467680
Pulled By: driazati
fbshipit-source-id: 13a14da87714325cc4c3d49e5fde8a850d5d757b
