[test-runner-*] support for browser context properties

[LarsDenBakker]

With test runner commands we allow setting certain browser properties, such as the window size or emulating media queries. However we are not able to change a lot of properties on the fly, for example touch support or the user agent on playwright. You can see a full list of all supported context properties here: https://playwright.dev/#version=v1.3.0&path=docs%2Fapi.md&q=browsernewcontextoptions

To support this we need a way to specify these properties separately from the test file, since they need to be configured before the page is created.