[Feature Request] Using Polars for loading and dumping data about gokart HOT 3 OPEN

@takeyama0 Thanks for your suggestion! I think it’s great to support Polars too.

And I basically agree with @hirosassa ’s idea to minimize dependencies, but I’m a little bit concerned about moving pandas on extras because some common methods (like TaskOnKart.load_data_frame) already use pandas.

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@takeyama0 Thanks for your suggestion and implementation idea!
I'm positive with supporting polars for its good performance as you suggest.

IMO, I would like to move pandas and polars on python extras and raise import error when the users use pandas/polars features without import it.
It is because I think there's no application using both pandas and polars.

@Hi-king @ujiuji1259 @mski-iksm How do you think about this?

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@hirosassa , @ujiuji1259 Thank you for your replaying! I am glad to hear your positive feedback about supporting polars.

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