"One file output" option added for csv/json.

[keltia]

The default output for csv and json files by datafusion is to output a series of files inside a directory named as the output file. I find it quite inconvenient so I have added -o/--one-file option. I have switched to clapa long time ago so I'm not sure how to rename the option (I agree -o is not ideal) so feel free to change it 😁. Thanks a lot for bdt BTW, it beats writing it myself.

[kassemz]

Thanks @andygrove for creating this nice tool! and thanks @keltia you added what I was looking for!

What about -ns/--no-split or -s/--single-file as other options?

[keltia]

I renamed -o into -s and --single-file. I also added support for Zstd. And updated datafusion and tokio.

[andygrove]

@keltia Could you fix the merge conflicts?

[keltia]

Oh sorry, didn't see your request but I see you got it done, thanks for the merge!