Split out common folder into CommunityToolkit/Tooling repo

[michael-hawker]

We need to move our common folder's contents to the root of a new repository to act as a sub-module for Labs and other repositories. This will enable us to share the common infrastructure and work on it independently for more than one project at a time.

We'll want a separate build.yml file there to do some basic checksum... this kind of relates to some of the work called out in CommunityToolkit/Labs-Windows#365

Depends on CommunityToolkit/Labs-Windows#397