Smoke tests in nodejs

[DonJayamanne]

For #5912

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• [n/a] Has a news entry file (remember to thank yourself!)
• [n/a] Appropriate comments and documentation strings in the code
• Has sufficient logging.
• [n/a] Has telemetry for enhancements.
• [n/a] Unit tests & system/integration tests are added/updated
• [n/a] Test plan is updated as appropriate
• package-lock.json has been regenerated by running npm install (if dependencies have changed)
• [n/a] The wiki is updated with any design decisions/details.

[rchiodo]

[ericsnowcurrently]

Here's my initial review. It covers everything except:

• src/smoke/src/
• uitests/

Also:

• presumably src/smoke/vscode/ is the code we copied and should not be reviewed. Is that right?
• why are we keeping a .vsix in the repo (why not rebuild it where needed) and how are we going to keep it up to date?
• I'm not a fan of using the term "smoke tests" here. Smoke tests is the minimal subset of your full test suite that you can (relatively) quickly run to sanity-check the code base. This matters more for test suites that run on the order of days (or many hours). I'd expect the tests you've added to be called "ui tests". If some of them are also smoke tests, that's fine, but the whole set shouldn't be called "smoke tests".