Extend environment field in GraphQL to expose deploy freezes

What does this MR do and why?

This merge request exposes deploy_freezes in the environment field in GraphQL API.

Please note the following:

• There has been a discussion on whether to add deploy_freezes to the project or the environment field.
• We reached an agreement we add it now to environment for the MVC and add scopes to deploy freezes later.
• The business logic for how start_time and end_time is calculated is specified here.
• We use Gitlab::SafeRequestStore to cache the result of deploy_freezes as per the backend proposal.

Resolves backend part of #212460 (closed).

Query Example

projects(fullPath: `root/gitlab-212460`) {
  environment(name: "production") {
    deploy_freezes {        
      status
      start_cron
      end_cron
      start_time
      end_time
    }
  }
}

Response

{
  "data": {
    "project": {
      "environment": {
        "deployFreezes": [
          {
            "status": "INACTIVE",
            "startCron": "0 15 * * *",
            "endCron": "0 18 * * *",
            "startTime": "2022-11-30T14:00:00Z",
            "endTime": "2022-11-30T17:00:00Z"
          },
          {
            "status": "ACTIVE",
            "startCron": "0 12 * * *",
            "endCron": "0 22 * * *",
            "startTime": "2022-11-30T11:00:00Z",
            "endTime": "2022-11-30T21:00:00Z"
          }
        ]
      }
    }
  }
}

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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