RFR: 8358588: ThreadSnapshot.ThreadLock should be static nested class

[Alan Bateman]

On Wed, 4 Jun 2025 12:03:15 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> SonarCloud points out that ThreadLock class introduced by [JDK-8357650](https://bugs.openjdk.org/browse/JDK-8357650) can be turned into static nested class. I don't think this shows any real bug yet, as unreferenced enclosing class reference gets nowhere. But it would be nice to be extra crisp here.
> 
> Additional testing:
>  - [ ] Linux x86_64 server fastdebug, `serviceability/`

Not an issue but clearer to define it as a static class.

(I've fixed the labels on this PR as this is serviceability code).

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Marked as reviewed by alanb (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25638#pullrequestreview-2896719812