Create a Nuget package for the full SDK

[Sarabeth-Jaffe-Microsoft]

Microsoft.Build.Runtime only puts together MSBuild, it is not a full build environment. To be usable as a library, a package containing MSBuild, Nuget, C# compilers, compiler targets must exist.

We think the SDK is the right place to put this issue so that this package can be consumed by users & the CLI repo.

dotnet/msbuild#1096

[Forgind]

Old bug triage:
I think that's basically what the SDK is at this point, or alternatively BuildTools. Since this issue is 7 years old, it seems to have been resolved in the interim without closing this issue.