title: CommonSenseQA has missing and inconsistent field names
comments: Thanks for reporting, @vblagoje.
  
  I'm opening a PR to address this. 
body: ## Describe the bug
  In short, CommonSenseQA implementation is inconsistent with the original dataset.
  
  More precisely, we need to:
  
  1. Add the dataset matching "id" field. The current dataset, instead, regenerates monotonically increasing id.  
  2. The [“question”][“stem”] field is flattened into "question". We should match the original dataset and unflatten it
  3. Add the missing "question_concept" field in the question tree node
  4. Anything else? Go over the data structure of the newly repaired CommonSenseQA and make sure it matches the original
  
  ## Expected results
  Every data item of the CommonSenseQA should structurally and data-wise match the original CommonSenseQA dataset.
  
  ## Actual results
  TBD
  
  ## Environment info
  - `datasets` version: 2.1.0
  - Platform: macOS-10.15.7-x86_64-i386-64bit
  - Python version: 3.8.13
  - PyArrow version: 7.0.0
  - Pandas version: 1.4.2