Show loading spinner in design card while design is uploading

What does this MR do?

Currently, when a design upload in progress, the user is presented with the filename in the design card (captured in issue #12928 (closed))

This MR adds a loading spinner in the card while the design upload is in progress.

Additionally, a test has been added for this new loading state.

Demo

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