RFR: 8275240: Change nested classes in jdk.attach to static nested classes [v2]

[Serguei Spitsyn]

On Thu, 14 Oct 2021 06:59:12 GMT, Andrey Turbanov <duke at openjdk.java.net> wrote:

>> Non-static classes hold a link to their parent classes, which in many cases can be avoided.
>> Similar cleanup in java.base - [JDK-8261880](https://bugs.openjdk.java.net/browse/JDK-8261880)
>
> Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8275240: Change nested classes in jdk.attach to static nested classes
>   update copyright year

Marked as reviewed by sspitsyn (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/5904