allowing @web/test-runner watch mode to operate in non-interactive shells

[trusktr]

In a super repo with git submodules, this could be useful for running each project's tests in watch mode at the same time.

This probably just requires replacing the dynamic output with regular appending output, and just letting the tests all output to STDOUT in any order (group the outputs so that test failures are not interleaved (don't stream pieces at a time)), and disable the interactive options for debugging/focusing/etc.

I think that should do it. Maybe it is even easier: just remove interactive options?

[trusktr]

The probably better approach in a mono- or super-repo is to just run a single instance and have it pick up all the test files. That's probably better than running multiple web-test-runners in parallel.

Plus then the dev experience is better because interactive mode is enabled, any test can be debugged, etc.