Show file in tree on WebIDE open

What does this MR do?

This MR creates an action for showing a nested file, and triggers this when the web IDE is loaded.

Why was this MR needed?

#45703 (closed)

Screenshots (if relevant)

It works 🙂

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • [ ] Has been reviewed by a Backend maintainer
  • [ ] Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #45703 (closed)