feat: support direct numpy output

[jitingxu1]

The current to_numpy() in ibisml is based on a pandas dataframe: Convert ibis table to pandas dataframe, then to numpy. It is not efficient.

Some backend, like duckdb, could directly convert query result to a numpy array.

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Had some initial discussion in ibis triage, we decided to hold off until we encounter a specific use case before proceeding further.