Iterate data science walkthrough experiment

[luabud]

The idea is that we'd have when clauses to show the data science tiles when we detect there's a notebook file open.
Discoverability would be addressed by a Notebooks walkthrough provided by VS Code.

[luabud]

A/B test with:
Option 1 – ship only the “Python” and “Jupyter” walkthroughs with each extension (merge contents from “Python DS” into these)
Option 2 – ship the “Python DS” with both extensions, but ship it nestled under the primary walkthroughs for each extension (i.e. “Python DS” is only accessible via a link from the “Python” walkthrough for the Python extension, and as a link from the “Jupyter” walkthrough for the Jupyter extension)