Proposal: UPSTREAM.md -- better tracking of upstream code in the JDK

[Magnus Ihse Bursie]

> 22 apr. 2022 kl. 01:54 skrev Dalibor Topic <dalibor.topic at oracle.com>:
> 
> I would suggest following the practice of leaving the UPDATING file in proximity of the code of the dependency, but defining a common way to reference it in UPSTREAM.md, such
> 
> Updating-Instructions: $path

Obviously I failed completely in conveying that my suggestion is that this is a distributed idea, not a centralized. There should be multiple UPSTREAM.md files, one per project, located with the sources. 

That means that any existing UPDATING files will be kept in the same spot they already are (after all, we’re just talking about two projects in total here..), but renamed to match the UPSTREAM.md standard, and with a few additional formal headers added at the top. 

/Magnus