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

[David Holmes]

On Tue, 12 Oct 2021 07:20:14 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)

Seems trivially fine.

Thanks,
David

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Marked as reviewed by dholmes (Reviewer).

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