gtestify dce and fuser tests (#45055)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/45055
See https://github.com/pytorch/pytorch/pull/45018 for context.
Test Plan: Imported from OSS
Reviewed By: ZolotukhinM
Differential Revision: D23811085
Pulled By: suo
fbshipit-source-id: 45008e41f2394d2ba319745b0340392e1b3d3172
