feat(dataset): support Link type for dataset

[tianweidut]

Description

• [#756 subtask] support index-only dataset #897
• Starwhale Dataset 2.0 #756

Feature Show

• dataset build
  
  

  ❯ swcli dataset summary mnist/version/latest
  {
      'rows': 10000,
      'increased_rows': 10000,
      'unchanged_rows': 0,
      'label_byte_size': 10000,
      'data_byte_size': 7840000,
      'include_link': True,
      'include_user_raw': True
  }

• data load for mnist
  • 
  • 
  • 
  • 

Modules

• Client
• Python-SDK

Checklist

• run code format and lint check
• add unit test
• add necessary doc

[jialeicui]

LGTM