Add MR lead time data to GraphQL

What does this MR do?

Exposes the MR lead time information (originally implemented in the REST API in !52243 (closed)) through GraphQL.

Example request/response

With interval: ALL (default)

Query:

{
  project(fullPath: "root/release-test") {
    analytics {
      leadTime(from: "2021-01-01T00:00:00.000Z", interval: ALL) {
        nodes {
          from
          to
          value
        }
      }
    }
  }
}

Response:

{
  "data": {
    "project": {
      "analytics": {
        "leadTime": {
          "nodes": [
            {
              "from": "2021-01-01",
              "to": "2021-02-12T16:47:43+00:00",
              "value": 3840
            }
          ]
        }
      }
    }
  }
}

With interval: MONTHLY

Query:

{
  project(fullPath: "root/release-test") {
    analytics {
      leadTime(from: "2021-01-01T00:00:00.000Z", interval: MONTHLY) {
        nodes {
          from
          to
          value
        }
      }
    }
  }
}

Response:

{
  "data": {
    "project": {
      "analytics": {
        "leadTime": {
          "nodes": [
            {
              "from": "2021-02-01T00:00:00Z",
              "to": "2021-03-01T00:00:00Z",
              "value": 3840
            }
          ]
        }
      }
    }
  }
}

With interval: DAILY (this will be what the UI uses)

Query:

{
  project(fullPath: "root/release-test") {
    analytics {
      leadTime(from: "2021-01-01T00:00:00.000Z", interval: DAILY) {
        nodes {
          from
          to
          value
        }
      }
    }
  }
}

Response:

{
  "data": {
    "project": {
      "analytics": {
        "leadTime": {
          "nodes": [
            {
              "from": "2021-02-05",
              "to": "2021-02-06",
              "value": 5037
            },
            {
              "from": "2021-02-10",
              "to": "2021-02-11",
              "value": 1446
            }
          ]
        }
      }
    }
  }
}

When the user doesn't have permission or the feature isn't licensed

Query:

{
  project(fullPath: "root/release-test") {
    analytics {
      leadTime(from: "2021-01-01T00:00:00.000Z", interval: DAILY) {
        nodes {
          from
          to
          value
        }
      }
    }
  }
}

Response:

{
  "data": {
    "project": {
      "analytics": {
        "leadTime": null
      }
    }
  }
}

When an error occurs

Query:

{
  project(fullPath: "root/release-test") {
    analytics {
      leadTime(from: "2020-01-01T00:00:00.000Z", interval: DAILY) {
        nodes {
          from
          to
          value
        }
      }
    }
  }
}

Response:

{
  "data": {
    "project": {
      "analytics": {
        "leadTime": null
      }
    }
  },
  "errors": [
    {
      "message": "Date range is greater than 91 days",
      "locations": [
        {
          "line": 4,
          "column": 7
        }
      ],
      "path": [
        "project",
        "analytics",
        "leadTime"
      ]
    }
  ]
}

Authorization

This new GraphQL data is available to projects on GitLab Ultimate and users with at least Reporter permissions. This matches the counterpart REST API.

Other changes

This MR deprecates the project.pipeline_analytics field in favor of the new project.analytics.pipeline. This groups all project analytics under the same field. The deprecated field is not removed and will continue to function as usual, so this will not affect end-users in any way.

Related to #291746 (closed)