Building a test project should also build the leaf's source project

[ViktorHofer]

Currently test assemblies that test inbox libraries don't build the leaf's source project. We have seen numerous cases where devs are jumping between building the source project and then building and invoking the test project. We should optimize this case by (incrementally) building the source project and its dependencies as well.

If developers only interact with a test project and don't want any incremental build to happen, they can pass --no-dependencies onto the CLI.

Tagging subscribers to this area: @safern, @ViktorHofer
See info in area-owners.md if you want to be subscribed.