add a minimal example of a remote workload using speedometer as a package

[bgrins]

This is copying the minimal set of changes from #456 necessary to wire up a trivial workload (followup from discussion in this thread: https://github.com/WebKit/Speedometer/pull/456/files#r1852664786)

The speedometer package is installed via

    "dependencies": {
        "speedometer": "../../"
    },

and then the workload consumes a single file from it import { ... } from "speedometer/resources/workload-testing-utils.mjs". Then when you npm run build it's able to do manage all of the necessary imports within speedometer itself to share code without needing to copy/paste into the files from the runner.

We may want to first land something like this, and then follow up with a smaller change for the Next integration, if there are additional complications with that.

[bgrins]

This can be previewed at https://remote-helloworld--speedometer-preview.netlify.app/?developerMode=&suites=Remote-Helloworld

[bgrins]

There will need to be some kind of unification with the helper / Page / PageElement methods so the convenience functionality like dispatchMouseEvent etc is made available to remote tests.

The simplest thing might be to export the entire classes from a shared module and make them available to both contexts, though I think there's a desire to get rid of them (instead relying on helper functions that take in the actual element).

I don't have a strong opinion on how this is resolved, but I think it could be done in a followup.

[bgrins]

I'll close this one since #456 has (mostly) incorporated the approach

[flashdesignory]

thanks - this was super helpful though!