[Backend MVP] Root-cause analysis of failing pipeline job

What does this MR do and why?

Adds the service which fetches the root cause AI data async and saves it in a redis cache

The data is the returnable via a graphql query which can be polled by the frontend.

https://gitlab.com/gitlab-org/gitlab/-/issues/411603

Screenshots

How to set up and validate locally

mutation ajf {
  aiAction(input: {analyzeCiJobFailure: {resourceId: "gid://gitlab/Ci::Build/342"}}) {
    requestId,
    data,
    errors
  }
}

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.