RFR: 8374984: Convert workerUtils to use Atomic<T>

[Stefan Karlsson]

On Tue, 13 Jan 2026 17:50:39 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this change to make SubTasksDone and SequentialSubTasksDone use
> Atomic<T> instead of AtomicAccess.
> 
> Testing: mach5 tier1

Marked as reviewed by stefank (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/29201#pullrequestreview-3659466935