Add Docs for vue-test-utils

What does this MR do?

Update Vue Testing docs to endorse vue-test-utils. Also rework Vue docs a bit and removed some duplication.

What are the relevant issue numbers?

Closes #41069 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides