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

[Andrey Turbanov]

> 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

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5904/files
  - new: https://git.openjdk.java.net/jdk/pull/5904/files/70cb33a9..06fcaa48

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5904&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5904&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5904.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5904/head:pull/5904

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