### Description
This change moves most - if not all - the logic, assemblies, build tasks, targets and props into NuGet packages. This allows .NET MAUI to be usable without having to care about what version of the workload is installed.
There are still a few things - mostly the automagic and Windows fixes - in the workload pack, but this is probably temporary and/or non-essential for the working of the build. Things like the project capabilities are still in the workload as this is needed for the IDE and cannot be in NuGet packages.
Everything else is now inside a NuGet package that can be upgraded, pinned and otherwise used without requiring VS to have installed the workload to match. There is the benefit of the NuGet packages being installed on disk and thus reducing/removing the need to download. But that is minimal now since we have smaller and fewer packages.
Scott Banning
Matthew Leibowitz
Sean Killeen