Consider exposing more APIs via RuntimeInformation

[pranavkm]

The CLI and AspNet Core have a bunch of APIs that p/invoke to read runtime information that's not readily available via RuntimeInformation. This includes operating system version and Unix distro name. Scanning through the code, there're internal APIs to read both these pieces of information, but they aren't surfaced in a way that can be consumed.

Could the API surface for RuntimeInformation be enhanced to include this information?

[joshfree]

@weshaggard giving this to you since you have strong feelings about this space

[weshaggard]

A more general issue is at https://github.com/dotnet/corefx/issues/12737 so closing this one in favor of that issue.