RFR: 8344853: Parallel: Improve comments in psParallelCompact

[Zhengyu Gu]

On Fri, 22 Nov 2024 10:39:31 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial revising some existing comments and adding some comments. No real code change other than a renaming.

LGTM

-------------

Marked as reviewed by zgu (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/22318#pullrequestreview-2458619392