feat: add DataFrame.to_arrow to create Arrow Table from DataFrame

[tswast]

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Towards #735 🦕

[snippet-bot]

Here is the summary of changes.

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• samples/polars/create_polars_df_with_to_arrow_test.py:17, tag bigquery_dataframes_to_polars

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[chelsea-lin]

LGTM

[chelsea-lin]

Is this file auto generated from a template? If not, can we update the copyright year to 2024? Also check other new files too?

[tswast]

This is templated, so not much we can do.

[chelsea-lin]

Can we assert polars_df is equal to bf_df? Or maybe there are some diverse?

[tswast]

We could possibly compare shapes or some aggregate values. I'll give it a try.