Show issue limits in board lists

What does this MR do?

Adds some basic style changes and functionality for #11403 (closed).

Screenshots

Backend work is still in progress so this MR will handle a minor update in style for the board list header. When the backend MR is merged in this MR will handle the styling and logic specified in the ticket when max_issue_count is set.

Note: FF has not been set up yet, thats why you can see the settings icon, WIP guarding that.

Functionality when FF is turned on, backend is merged in, and a user can set WIP Limits(this will not be for a little while).

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

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