Add pipeline status subscription

What does this MR do and why?

The purpose of this MR is to implement a subscription for front end views to be able to access real time updates on a pipeline status. This will initially be used for real time updates on the pipeline status icon in the latest commit widget on the main repository page.

• ciPipelineStatusUpdated requires a global pipeline id to initiate the subscription.
• the subscription is triggered when any transition event occurs on the pipeline's status
• the subscription payload is a Ci::PipelineType

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Example Subscription query:

subscription pipelineStatusUpdated($pipelineId: CiPipelineID!) {
  ciPipelineStatusUpdated(pipelineId: $pipelineId) {
    iid
    status
    detailedStatus {
      detailsPath
      name
      tooltip
      label
      favicon
    }
  }
}

NOTE: You will need to set a pipelineId variable or you can pass it directly. The value required is a pipeline gid( ie. "gid://gitlab/Ci::Pipeline/1234"). You can also get the pipeline's formatted gid in the rails console by calling to_gid on an existing pipeline.

Steps to test and validate locally:

1. Ensure you are logged into your local instance and navigate to the graphql explorer page (eg. http://gdk.test:3000/-/graphql-explorer or relace gdk.test:3000 to whatever your localhost is set to)
2. In your terminal start a rails console (bundle exec rails c)
3. In the console find a pipeline you would like to use for testing and fetch the global id:

 pipeline = Ci::Pipeline.last 
 pipeline.to_gid.uri.to_str #this is the string you will use for the $pipelineId variable in the graphql UI

4. Return to the graphql explorer and copy the query noted above ⬆️ before the steps
5. Set the pipelineId variable to the global id string you generated in the console in Step#3 (you can do this either directly in the subscription query or in the section below the query box that allows you to input variables:

{
  "pipelineId": "gid://gitlab/Ci::Pipeline/???" #replace with the string you generated in the console
}

6. Press the play ▶️ in the graphql-explorer UI. The initial response should be nil because you are initiating/opening up the subscription. You should see this response:

{
  "data": {
    "ciPipelineStatusUpdated": null
  }
}

7. There are 2 ways to trigger the subscription from the rails console to test it out. Using the same pipeline set earlier (pipeline = Ci::Pipeline.last) :

i. Triggering the subscription directly: GraphqlTriggers.ci_pipeline_status_updated(pipeline)

ii. Mocking a pipeline state machine event with any valid action(depending on the current state of your pipeline the actual status may update or not): pipeline.cancel!

8. With either of the actions performed in Step#7 the subscription response should update with the values you set in the subscription and the data response should look something like:

{
  "data": {
    "ciPipelineStatusUpdated": {
      "iid": "40",
      "status": "CANCELED",
      "detailedStatus": {
        "detailsPath": "/gitlab-org/gitlab-shell/-/pipelines/571",
        "name": "CANCELED",
        "tooltip": "canceled",
        "label": "canceled",
        "favicon": "favicon_status_canceled"
      }
    }
  }
}

Gotchas: If you are getting and unauthorized error make sure the user you are logged in as is authorized to read the pipelien/project, probably best to be logged in as the root user.

Related to #516247 (closed)