Ensures unique file names for merge requests

What does this MR do?

Related issue: #339214 (closed)

This ensures that the file name is always unique for the merge request being created to avoid merge conflict issues when the spec retries.

Conformity

• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.