taming resource scopes

[Maurizio Cimadamore]

Hi,
we've been looking beyond 17 at things we can do to improve support for 
resource scopes, especially in the context of native calls. I tried to 
capture the various things we explored in the writeup below:

https://inside.java/2021/05/28/taming-resource-scopes/

I think overall the takeaway points are pretty good:

* we can simplify the acquire/release scope mechanism with a better, 
higher-level API
* we can enhance safety when calling native functions using _any kind_ 
of resource scopes (with relatively little overhead)
* we can make it easier to tailor the safety characteristics of CLinker 
to suit application needs

Cheers
Maurizio