Need to look for Directory.Build.props / Directory.Packages.props and detect changes there too

[Aaronontheweb]

See akkadotnet/akka.net#6825 (review) - unfortunately, these .Props files are implicitly referenced (rather than explicitly) so we're going to need to add a special case for them.

Any projects that are descended from a folder with one of these files (Directory.Build.props / Directory.Packages.props) are going to be affected by those changes.