Resolve "Add checklist count to work item description"

What does this MR do and why?

Adds the existing checklist count element to the work item description (/work_items/iid and drawer) so it matches the legacy issue view (/issues/iid) .

MR acceptance checklist

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

FYI: This is not a new feature. It's already used on the /issues/iid page , so the behavior should be the same.

For both views, the issues_list_drawer flag should be enabled.

1. Open or create an issue with a checklist in the description
2. Expect that once created, the x of x items completed section appears under the description
3. Expect that whenever a check is marked, the count updates
4. Expect that when all checks are marked, a checkmark appears
5. Expect it appears before the edited by ... sentence and on the same line

1.Go to the issues list page

1. Click on the issue with the checklist
2. Expect the work item drawer opens
3. Expect that the checklist count also is visible on that view

Related to #461413