Adds create lifecycle mutation

What does this MR do and why?

This code change adds a new feature to create custom work item lifecycles in GitLab. A lifecycle defines the different statuses that work items (like issues or tasks) can have as they progress through a workflow.

The main additions include:

1. New API endpoint: A GraphQL mutation called lifecycleCreate that allows users to create custom lifecycles with their own set of statuses and default settings.

2. Feature flag support: Added a new feature flag check for work_item_status_mvc2 to control access to this experimental functionality.

3. Service layer: Created a new CreateService that handles the business logic for creating lifecycles, including validation, permission checks, and automatic conversion of system-defined lifecycles to custom ones.

4. Enhanced base functionality: Improved the shared base service to better handle status management, tracking user actions, and ensuring proper data relationships.

5. Documentation: Updated the API documentation to describe the new mutation, its parameters, and return values.

References

1. BE: Add mutation to create lifecycle (#548456 - closed)
2. BE: Convert to custom statuses when create life... (#559001 - closed)

Screenshots or screen recordings

How to set up and validate locally

mutation LifecycleCreate($input: LifecycleCreateInput!) {
  lifecycleCreate(input: $input) {
    lifecycle {
      id
      name
      statuses {
        id
        name
        iconName
        color
        __typename
      }
      defaultOpenStatus {
        id
        name
        __typename
      }
      defaultClosedStatus {
        id
        name
        __typename
      }
      defaultDuplicateStatus {
        id
        name
        __typename
      }
      workItemTypes {
        id
        name
        iconName
        __typename
      }
      __typename
    }
    errors
    __typename
  }
}

{
  "input": {
    "namespacePath": "jashkenas",
    "name": "New lifecycle",
    "statuses": [
      {
        "name": "New to do",
        "category": "to_do",
        "color": "#ffffff"
      },
      {
        "name": "New Done",
        "category": "done",
        "color": "#ffffff"
      },
      {
        "name": "New Duplicate",
        "category": "canceled",
        "color": "#ffffff"
      }
    ],
    "defaultOpenStatusIndex": 0,
    "defaultClosedStatusIndex": 1,
    "defaultDuplicateStatusIndex": 2
  }
}

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