V8 coverage API next steps

[joyeecheung]

Opening an issue to track the work before moving v8.startCoverage() and v8.stopCoverage() out of experiment. This will take some refactoring. See #33807 (comment) and #33807 (comment)

1. Add a v8.startCoverage() method to reuse the per-env connection, if NODE_V8_COVERAGE is not set (would be useful to restart after v8.stopCoverage())
2. It would be good to have an API that (optionally?) returns the coverage result. I think it should be v8.takeCoverage() as the Profiler.stopPreciseCoverage command doesn't return this but the Profiler.takePreciseCoverage does. Also, I realize that this method should be asynchronous as there's no guarantee that we can get the response from inspector synchronously (it just happens to be this way right now), so it should probably return a promise.
3. Error reporting can be improved (return a rejection?)

Also #35212