Fix and add more padding mode support for Conv (#31784)
Summary:
Fix https://github.com/pytorch/pytorch/issues/29712 #29668 , add arg checking, doc, and support for reflection and replication padding modes.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31784
Differential Revision: D19301974
Pulled By: ezyang
fbshipit-source-id: a0ed4815c0c22e416b16e256bba04324e376b2f8
