DCR: Review ReferenceCountedDisposable as an alternative to IRetainable

[jkotas]

From @ahsonkhan on September 7, 2017 20:26

Design Change Request (DCR)
From dotnet/coreclr#13583 (comment):

💡 My strongest recommendation here would be to carefully review the semantics of ReferenceCountedDisposable<T> in Roslyn and consider how they might be usable in these scenarios as an alternative to IRetainable. This type provides strong guarantees in concurrent code and eliminates many concerns related to ownership when both IDisposable and IRetainable are at play. It also provides a weak reference type with strong semantic guarantees.

cc @KrzysztofCwalina, @shiftylogic

Copied from original issue: dotnet/coreclr#13840

[joshfree]

Reviewed offline with feature team; closing suggestion issue and sticking with current design shape. If you'd like to create an API proposal we can follow up further. Thank you