Properly expose import errors in new Vue-based UI

What does this MR do?

Related issues: #22035 (closed) #38418 (closed)

This MR adds server generated error message when importing project to flash

Before:

After:

## 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.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done