Add validation for move action in SnippetInputAction

What does this MR do?

For the move action, we have to ensure that the previous_path and the file_path in the SnippetInputAction class are different. Otherwise, the repository will raise a commit action error.

At the moment, there is no need to translate the validation errors because they're not displayed to the user.

Refs #218516 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content