[test-runner-commands] implement command for choosing option from <select>

[WickyNilliams]

Essentially, this would expose the following API https://pptr.dev/#?product=Puppeteer&version=v10.4.0&show=api-elementhandleselectvalues

I assume a similar API is available in other browsers/web drivers.

Without this, it is quite awkward to choose a value from a <select>. Of course you could just set its value prop, but then you don't get an accompanying change event.

The command API could look something like this:

const select = document.querySelector("select")
await selectOption(select, "1")