Display message on file backup pipeline error

What does this MR do?

This MR adds more verbose error logging when file backups fail on run_pipeline!. Currently the only message displayed in this scenario is Backup failed, which makes it difficult to debug issues such as #27220 (closed).

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.