Return empty Arrow table instead of None

[JakobGM]

I have created no issue because the PR itself should be descriptive enough, the discussion can perhaps be taken here instead?

In the same way that SnowflakeCursor.fetch_pandas_all() now returns an empty DataFrame with the correct schema when the query produces 0 rows, SnowflakeCursor.fetch_arrow_all() should do the same.

[github-actions[bot]]

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[JakobGM]

I have read the CLA Document and I hereby sign the CLA