fixing conv2d decomposition and tests (#70127)
Summary:
Current implementation has a bug where decomposed `add_optional` from `conv2d` is placed before the producer node, this causes linter error on graph.
Cherry-picked from https://github.com/csarofeen/pytorch/pull/1333
Fixing issue posted in https://github.com/csarofeen/pytorch/issues/1325
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70127
Reviewed By: ejguan
Differential Revision: D33199018
Pulled By: jansel
fbshipit-source-id: bce1f14a443811b4d55116a04fd4daa86084cc47
