Batch operations support

[Xuanwo]

As required by #279

It could be great for us to have native batch operations support.

Maybe we can have a BatchOperator which can:

• Specify the workers
• Create/Start/Stop/Resume batch operations?
  • Maybe this is too heavy, we can start by creating and starting batch operations.

Batch operations include:

• Delete a dir recursively
• Copy a dir (Can we adopt server-side copy if backend support it)
• Move a dir

[Xuanwo]

Generate a list of futures that allow users to decide how to execute them

[Xuanwo]

Databend have to implement this feature byself: databendlabs/databend#5809

[Xuanwo]

I'm working on a demo now!