* Use the `FrameworkAdapter` interface provided by the Kotlin/JS test
  infra, so that failed tests are correctly reported for the JS target
  on Node.js (does not apply to Wasm/JS, which does not require
  "adapter transformation").
* Use JS Promise instead of callbacks to interact with the JS test
  framework.
* Clean up the code to avoid API layers changing from Mocha/Jasmine
  style ("describe", "it) to Kotlin test style ("suite", "test) and
  back.