Resolve "Work items list [FE] - Add "Email a new issue to this project""

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What does this MR do and why?

A frontend split from !199897 (merged) to resolve !199897 (comment 2682292698)

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. In rails console enable the feature flag Feature.enable(:work_item_planning_view)
2. Set incoming_email.enabled:true in config/gdk.yml and gdk restart
3. Visit any project pages such as http://gdk.test:3000/toolbox/gitlab-smoke-tests/-/work_items
4. Scroll down and click Email a new work item to this project

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #536880 (closed)