Add support for editing feature title

What does this MR do and why?

Note: Work Items are currently behind feature-flag and can be enabled by running Feature.enable(:work_items) in rails console. Once done, visit /gitlab-org/gitlab-test/-/work_items/1 on your GDK to access sample work item.

Adds support for inline editing of a feature title.

Screenshots or screen recordings

Edit Work Item Title

How to set up and validate locally

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

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #334808 (closed)