Some of the npm audit warnings left after #13897 require an updated `mocha` version to remedy. As we only really use `mocha` to do unit-testing, it should be safe to update if all of our existing tests pass with the new version.
Test-bot: skip
This change renames the test files for Web according to the discussion at
the Keyman conference in November 2024. It also renames some folders from
`test` to `tests`.
