Get rid of product.__wptrunner__

[gsnedders]

This is something that I've mentioned in various PRs when we've been refactoring code around this; #13966 changed the loading side to create an object, but really this object should be created within the browser module.

There are a number of reasons to do this, partly code cleanliness, but perhaps the most useful feature would be to make it possible to change the executor for a browser based on command line args, thereby avoiding having to duplicate the browser for multiple executors (as we currently have for Edge, and will soon have for Chrome).

[foolip]

@gsnedders I'll downgrade the prioritiy of this since it hasn't shown up in our planning and doesn't have an assignee.

[gsnedders]

@foolip I've expanded the description here; I'd probably say it's something we should definitely do as part of the Chrome/CDP work (so it's a command line argument rather than a separate product).

[foolip]

Will it still be possible to have separate expectations in infrastructure/ for different executors?

[jgraham]

We may need to change things so that the expectations can be per-browser or per-executor, but that's possible to do.