Add fallback to BF16 support check (#7754)
When DeepSpeed is installed without `--no-build-isolation`, `torch_info`
contains placeholder values ('0.0') causing BF16 tests to incorrectly
skip.
This PR adds runtime fallback detection for torch, NCCL, and CUDA
versions when stored values are invalid.
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Signed-off-by: Masahiro Tanaka <mtanaka@anyscale.com>
