Epic Board - Fetch and display empty lists [RUN AS-IF-FOSS]

What does this MR do?

• Fetch lists for current epic boards
• Render empty lists
• Query to fetch epics in lists (epics do not display in this iteration)

Requires :epic_boards feature flag.

To facilitate review, the fetching and displaying of epics in board in being split into 2 MRs, this one being the first one. For extra context, a full draft displaying epics in lists is available here: !54171 (closed)

In this iteration, empty lists display and fetching of epics "fails" displaying an error message. This error message is temporarily inherited from issue boards and will be updated in the next iteration.

Notable changes to make boards more generic:

• Action fetchIssuesForList renamed to fetchItemsForList
• Mutation REQUEST_ISSUES_FOR_LIST renamed to REQUEST_ITEMS_FOR_LIST
• Mutation RECEIVE_ISSUES_FOR_LIST_SUCCESS renamed to RECEIVE_ITEMS_FOR_LIST_SUCCESS
• Mutation RECEIVE_ISSUES_FOR_LIST_FAILURE renamed RECEIVE_ITEMS_FOR_LIST_FAILURE
• More renaming will happen in the next iteration, as the impact is quite large

Progress of Epic boards feature development

Previous iterations	MR link
Index page	!53100 (merged)

Screenshots (strongly suggested)

By default	After manually creating a label list

Example query to create a label list for local testing

mutation {
  epicBoardListCreate(input: {boardId: "gid://gitlab/Boards::EpicBoard/3", labelId: "gid://gitlab/GroupLabel/65"}) {
    list {
      id
    }
  }
}

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #233438 (closed)