Repo Editor : Fixes Back Button for files + line number jumping for preview and editor

What does this MR do?

It fixes the back button behavior in the Repo Editor. It also cleans up the sidebar tests so it is not firing multiple events. The reset of the path in the MR_Service test is to prevent an unhandled promise rejection error in the future.

Why was this MR needed?

So we support Back button

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

#36436