chore(smoke-tests): make smoke tests easier to run locally

[jtoar]

@Tobbe tried to run the smoke tests locally last week and ran into some trouble since I didn't fix how we run them locally after making my changes in #8449. This PR fixes that by adding a script in tasks that runs smoke tests somewhat interactively:

smoke-tests.mov

A few more note:

• I added back the env var PROJECT_PATH. I still think it's too vague, but I shouldn't have broken the way it works
• I didn't show it in the video to save time, but I made "all" an option to run all the smoke tests. It just runs them one after another. No more reading interleaved logs
• This script even warns you if you forgot to build before running prerender or serve!
• Nice help output via --help or -h: