Decouple file row from IDE

What does this MR do?

This makes the file row component from the Web IDE into a re-usable component which will allow it to be used inside of the merge request changes tab.

What are the relevant issue numbers?

Pre-request to https://gitlab.com/gitlab-org/gitlab-ce/issues/14249

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides