Extract information about the release tag, number of commits since the tag and the hash of the latest commit within a MSBuild target, and bake that information into version properties of the assemblies appropriately.
`AssemblyVersion` and `FileVersion` are now inferred from the `Version` property, which is inferred by `VersionPrefix`. So now both `AssemblyVersion` and `FileVersion` are 6.0.0.0 for each of PowerShell assemblies, and the `ProductVersion` and `InformationalVersion` are 6.0.0.
