Running extension test via Test Explorer

[rebornix]

• Running unit test in builtin Test Explorer is all fine
• 🏃 Running extension tests has some road bumps (e.g., missing Python extension)

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR).
• Title summarizes what is changing.
• Appropriate comments and documentation strings in the code.
• Has sufficient logging.
• Has telemetry for feature-requests.
• Unit tests & system/integration tests are added/updated.
• Test plan is updated as appropriate.
• package-lock.json has been regenerated by running npm install (if dependencies have changed).