Currently this code expects a "url string", rather than a proper `URL` instance, which seems completely unnecessary now. The explanation for this is, as so often is the case, "historical reasons" since a lot of this code predates the general availability of `URL`.
Given that there's no less than *five* different, but very similar, implementations this helps reduce code duplication and simplifies maintenance.
Also, spotted during rebasing, pass the `enableHWA` option "correctly" (i.e. as part of the existing `transportParams`) to the `WorkerTransport`-class to keep the constructor simpler.
