RFR: 8370406: Parallel: Refactor ParCompactionManager::mark_and_push

[Francesco Andreuzzi]

On Wed, 22 Oct 2025 08:26:10 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple refactoring to reduce indentation level and inlining a single-caller method.
> 
> Test: tier1-3

Marked as reviewed by fandreuzzi (Author).

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PR Review: https://git.openjdk.org/jdk/pull/27933#pullrequestreview-3364313653