Add support for building / testing new features in Dev Home without impacting existing customers

[adrastogi]

Suggested new feature or improvement

This issue tracks creating a mechanism for new longer-lead features to be added to the application without impacting the current experience.

Scenario

If the Dev Home team wanted to experiment with building / offering new experimental functionality, this feature would enable them to do so without having those features lit up for Preview / Stable customers until they are ready.

Example: we want to build a new foo tool for the application. It is a complex tool that will require a lot of iteration and testing (i.e., multiple months). We don't want customers to see a half-baked feature slowly come to life in the app, so we need some way to work on this new tool in the codebase without causing any impact to Preview customers.

Additional details

Related work done in Terminal: microsoft/terminal#10361