modify emit() of TopK to emit on batch_size rather than batch_size-1

[JasonLi-cn]

Which issue does this PR close?

Closes #.

Rationale for this change

Simply modify the logic of "break into record batches as needed". This modification avoid generating an empty RecordBatch where the batch.num_rows() eq batch_size.

https://github.com/apache/arrow-datafusion/blob/03d8ba1f0d94bac6bb8bb33e95f00f9f6fb5275a/datafusion/physical-plan/src/topk/mod.rs#L210-L219

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[alamb]

makes sense to me -- thank you @JasonLi-cn

[alamb]

(BTW @JasonLi-cn I am not sure what is inspiring all your work recently to optimize DataFusion but it is much appreciated 🙏 )

[Dandandan]

Thanks @JasonLi-cn

[JasonLi-cn]

(BTW @JasonLi-cn I am not sure what is inspiring all your work recently to optimize DataFusion but it is much appreciated 🙏 )

I have been using DataFusion and arrow-rs since 2021, but most of my work has been on developing TableScan or upper-level applications, as well as some optimizations for specific scenarios. My current work is mainly focused on performance optimization (which is also my interest) and feature enhancement, and I think it is necessary to contribute the improvements directly to the community, which is beneficial for the healthy development of both DataFusion and our own projects.
My PR may not be perfect, and I also thank all the community friends for their suggestions, from which I have learned a lot 🙏.

[alamb]

My current work is mainly focused on performance optimization (which is also my interest) and feature enhancement, and I think it is necessary to contribute the improvements directly to the community

100%

My PR may not be perfect, and I also thank all the community friends for their suggestions, from which I have learned a lot 🙏.

I think this describes everyone here (including myself!) I also learn a lot from interacting with other developers and working with the communnity