[Arrow] bf16 support in arrow

[changhiskhan]

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🚀 The feature, motivation and pitch

We're working on supporting bf16 in lance format, which will be presented as a bf16 extension type in Arrow (see PR for details: https://github.com/lancedb/lance/pull/1002).

We're considering contributing the Arrow extension type as a canonical extension to the Arrow project. Would this be of interest / value to the pytorch community? How would this be integrated into the pytorch library?

If y'all are interested, we could start a discussion thread on Arrow mailing list and chat together?

Alternatives

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Additional context

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cc @SsnL @VitalyFedyunin @ejguan @dzhulgakov