Add unsafeRemoveConstant for ClassType (#30787)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30787
This is needed when we fuse conv bn modules,
where we need to rewrite a constant bias (None) of conv to an attribute
bias of Tensor
Test Plan:
build/bin/test_jit
Imported from OSS
Differential Revision: D18846850
fbshipit-source-id: 9fd5fe85d93d07226e180b75d2e068fe00ca25fe
