Close feature spec gap for work items

Follow-up from #388612 (closed)

As #388612 (closed) focused on OKRs, we're missing a few tests for work item features:

1. Tests for work items in modals
2. Testing title changes, milestone widget
3. Better testing around different use cases of using either global ID or internal ID
4. Generally, we want a test coverage that is as good as for Epics and Issues right now (e.g. quick actions etc.)