Multiple fixes for functional collectives. (#95897)
_functional_collectives.py: Ensure we always wait all collectives.
derivatives.yaml: mark all_reduce as non differentiable
gen_variable_type.py: Add all_reduce to DONT_ENFORCE_TENSOR_IMPL_USE_COUNT
common_dtensor.py: replace dist.barrier with all_reduce
Pull Request resolved: https://github.com/pytorch/pytorch/pull/95897
Approved by: https://github.com/wconstab, https://github.com/fegin
