Preserve params for work items calendar and RSS endpoints

What does this MR do and why?

This MR fixes an issue where the calendar / RSS options in the new work items lists would ignore any filtering params passed to them. The behaviour here mimics that of the legacy issues list.

References

• https://gitlab.slack.com/archives/C02403NRD40/p1759170038677099

Screenshots or screen recordings

Not provided

How to set up and validate locally

Prerequisites: enable the work_items_group_issues_list FF

We'll use labels here to test the filtering logic, but the behaviour should apply using any filters

1. Navigate to the project issues list
2. Create a new issue. Set the due date to tomorrow's date, and create a new label from the new issue dialog. In this example, we'll title the label A
3. Create another issue. Set the due date to tomorrow's date, but don't give the new issue a label
4. In the filter bar, filter by Label is A. You should see only the first issue you created in the list
5. Refresh the page*
6. In the ⋮ menu on the top right, select Subscribe to RSS feed
7. Observe that only the first issue created is returned. You can confirm this by looking for the <label>A</label>. No other work items should be returned.
8. Navigate back in the browser, and select Subscribe to calendar in the ⋮ dropdown
9. Open the .ics file which is downloaded in a text editor. Observe again that only the issue with the label is returned.
10. Repeat the steps above in the group issues list. You can use the same label filtering and issues created in the project above

* The page refresh is required for the new filter criteria to apply. This appears to be an existing bug, since this also occurs in the legacy issue list pages

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