[ui] Test MSW to replace json-server in mock tests

### Change

Our mock tests are not very easy to configure. [MSW](https://github.com/mswjs/msw) has a new release that removes old deprecated calls, and its API appears to be clearer than json-server. Worth checking if we can use msw instead.
- https://news.ycombinator.com/item?id=37985777

### Are you interested in contributing a pull request for this task?

Yes

No files or tests are named; start by locating the mock tests and json-server configuration in Apache Jena. Compare whether MSW can replace the current setup, then verify that the mock test suite passes with the new configuration and that the setup is easier to maintain.

Written by the indexing model from the issue text.