Include .NET Core Runtime in WindowsDesktop bundle

[dagood]

To run a .NET Core WPF/WinForms app, you need to install both the .NET Core Runtime and WindowsDesktop Runtime. (As well as the correct x86/x64 bitness.) This is unexpected and is a significant pain point when trying to deploy FDE WinForms and WPF apps.

This issue tracks the incremental step of including the .NET Core Runtime dependency in the installer bundle for the WindowsDesktop Runtime.

This will bring our current matrix of 4 installers needed to run WindowsDesktop apps:

	x64	x86
.NET Core Runtime	x	x
.NET Desktop Runtime	x	x

down to 2:

	x64	x86
.NET Desktop Runtime	x	x

Then, later, we may be able to combine the x86/x64 ones as well by completing https://github.com/dotnet/core-setup/issues/7763. (This is more difficult from an implementation perspective.)

/cc @KathleenDollard @leecow @dleeapho @MichaelSimons @rowanmiller

[KathleenDollard]

👍 Yeah!

[dagood]

This is merged for 3.1 preview 2 with PR dotnet/core-setup#8508!

Waiting to gather data/feedback before potentially porting to the 3.0 servicing branch as well. (Not tracking that in this issue.)

Implementing it in 5.0+ has to be done separately in the dotnet/windowsdesktop repo, dotnet/windowsdesktop#20 tracks that.