text: Title: [BUG] Some KPI endpoints do not distinguish between failure and no data
  Body: ## Describe the bug
  
  Some KPI endpoints ([here](https://github.com/chaos-genius/chaos_genius/blob/ad6759f069462ef5b487e5b22172cccc28e49653/chaos_genius/views/kpi_view.py#L255)) do not return a `status` field indicating success or failure. Instead, they return a default value if an exception occurs inside the view. 
  
  ## Explain the environment
  - **Chaos Genius version**: all
  - **OS Version / Instance**: all
  - **Deployment type**: all
  
  ## Current behavior
  
  Described above
  
  ## Expected behavior
  
  The endpoints should return a `"status": "failure"` when an exception occurs and `"status": "success"` otherwise.
  
  ## Screenshots
  
  NA
  
  ## Additional context
  
  This is also present in the new RCA views introduced in #580.
  
  ## Logs
  
  NA