text: Title: Reusing 'parametrize' values?
  Body: Hi, is there any way to reuse parameterize values?
  
  For example, I have the following test configuration:
  
  ```yaml
  ---
  test_name: Successfully returns the auto registration history
  includes:
    - !include stage.async-result.yaml
  
  marks:
    - parametrize:
        key: vin
        vals:
          -  > A lot of values here <
  
  stages:
    - name: Trigger the task
      request:
        url: "http://localhost:8000/auto/history/{vin}"
        method: GET
      response:
        status_code: 202
        save:
          $ext:
            function: utils:url_from_refresh_header
    - type: ref
      id: async_result
  
  ---
  test_name: Successfully returns auto accidents
  includes:
    - !include stage.async-result.yaml
  
  marks:
    - parametrize:
        key: vin
        vals:
         -  > A lot of values here <
  
  stages:
    - name: Trigger the task
      request:
        url: "http://localhost:8000/auto/accidents/{vin}"
        method: GET
      response:
        status_code: 202
        save:
          $ext:
            function: utils:url_from_refresh_header
    - type: ref
      id: async_result
  ```
  
  How can I define the parametrize values in one place and reuse them?