Check project file references to assemblies outside packages folder

[naeemkhedarun]

As an engineer I want to see if there are any references to packages not defined in nuget So that I can fail the build when someone checks in an assembly that might not be available to other engineers So that I can reduce reliance on installed sdks which need to be rolled out on build agents

As an engineer I want to be able to set exclusions to the reference checker So that I can allow for using installed sdks which are not and cannot be made available via nuget