Explore a 'WSL stub' extension that guides users to install the WSL extension

[bamurtaugh]

Creating a public issues to track our progress on the WSL stub extension exploration/implementation.

[aeschli]

The VSCode build for Windows now contains the remote-wsl-recommender extension. It adds items to the remote menu helping users to install WSL and the Remote WSL extension.
All that is behind experiments, so we can find out what is most useful and user-friendly way to do so.

[joaomoreno]

@aeschli Should there be a TPI for this?

[aeschli]

@joaomoreno I will create one...