Add root level breadcrumb to "Your work" pages

What does this MR do and why?

Adds a "Your work" breadcrumb to all (*) "Your work" pages. See #399203 (closed).

(*) This is part 1 out of 2. It does not yet add the breadcrumb to the pages that are only available in EE. These are Environment Dashboard, Operations Dashboard and Security.

Screenshots or screen recordings

These are just some examples. Please check all pages in Your work.

How to set up and validate locally

• On your homepage (/) and any other page linked from the "Your work" sidebar (except the EE dashboards), check that the breadcrumbs start with "Your work >".
• Check also the "New project" and "New group" pages. They should start with "Your work > ..." as well.
• Also create, show and edit a snippet. These pages should also have "Your work > Snippets > ..." as their breadcrumbs.

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.