Use redirect for linked items when Service Desk issue

What does this MR do and why?

This change updates how work items (like tasks, issues, and incidents) behave when clicked in a relationship list. Previously, only incidents would redirect users to a new page when clicked, while other items would open in a modal popup.

Now, the system also redirects users to a new page for Service Desk issues (issues created by the support bot). The code adds logic to detect when an issue was created by the support bot user and treats it the same way as incidents - opening in a new page instead of a modal.

The changes include adding a new function to identify Service Desk issues, updating the database query to fetch author information, and expanding the tests to cover both incident and Service Desk issue scenarios. This ensures a consistent user experience for these special types of work items that need to open in their full page view rather than a simplified modal.

Solves Click from Linked items opens Service Desk issu... (#556193)

References

1. Click from Linked items opens Service Desk issu... (#556193)

Screenshots or screen recordings

Before	After
Screen_Recording_2025-07-17_at_16.26.46	Screen_Recording_2025-07-17_at_16.25.17

How to set up and validate locally

1. Enable incoming email with a mock mailbox. In config/gitlab.yml place this under the development section:

   incoming_email:
    enabled: true
    address: "incoming+%{key}@example.com"

2. Add a new issue

3. Add a second issue. Comment /convert_to_ticket user@example.com to convert it to a Service Desk issue. The page should reload.

4. Now mark the two issues as related.

5. From the regular issue click on the linked item. See it should now open with a reload/redirect instead of opening in the drawer or using the Vue router if drawer feature flag is disabled.

MR acceptance checklist

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