[Functionalization] Fix torch.distributed tests (#4477)
Summary:
This pull request tries to fix the following two tests:
1. test_allgather: allgather uses copy_ internally to update the input and copy_ being decomposed into copy which we need to lower.
2. test_send: send uses t.data to update t’s data which is not supported in functionalization. See functorch.functionalize doesn't allow t.data update pytorch#91093. After switching to copy_, it looks like the problem is fixed.
Test Plan:
CI.
