QuickActions::InterpretService handles group containers

What does this MR do and why?

Before, QuickActions::InterpretService would only be able to handle project level entities. Now that Issues/WorkItems can exist at the group level, Issuable related commands need a container group to scope queries like the one from the LabelFinder.

In .com this was causing a label finding query to timeout since it was completely unscoped to a group or project, so it was trying to find a huge amount of labels. Locally this wouldn't fail, but would effectively return a very long list of unscopped labels when trying to apply the /label quickaction

MR acceptance checklist

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How to set up and validate locally

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

1. In rails console enable the experiment fully

   Feature.enable(:namespace_level_work_items)

2. Visit any group work items list page such as http://127.0.0.1:3000/groups/flightjs/-/work_items
3. Create a new epic using the Create Epic button
4. On the newly created epic use the /label quickaction on a comment and make sure that returned labels in the autocomplete dialog are scoped to the group.
5. Apply the quickation and the label should be applied to the work item

Related to #441123 (closed)