Show work items correctly on activity feed

What does this MR do and why?

This MR fixes the activity feed and displays also activities related to work items.

Related issues/MRs:

• Set event type correctly for WorkItems creation (!93801 - merged) - when a new work item is created, target is Issue and this MR fixes that
• Events for work items (#369411) - we need to unify way we handle events for work items

How to set up and validate locally

1. Run rails console rails c
2. Enable work items related feature flags: Feature.enable(:work_items) and Feature.enabled(:work_items_create_from_markdown)
3. Go to an issue
4. Create a task list in the description, save the issue
5. Create a task using the button in the task list in the issue description
6. Close that task
7. Check your activity feed
8. You should see that you opened an issue (fix: !93801 (merged)) and that you closed the work item (this is the fix in this MR)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #366206 (closed)