Display blocking issue count on issues in haml issue list

What does this MR do?

The feature in this MR sits behind :blocking_issues_counts FF.

• Adds blocking issues count badge and the ability to sort by "blocking" in issue list view.
  • blocking issue counts: #217569 (closed)
  • issue list view: #34247 (closed)

Screenshots

Blocking issues count badge

Sort by "blocking" demo

Sort by "Blocking"

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