RFR: 8332841: GenShen: Pull shared members from control thread into common base class

[Y. Srinivas Ramakrishna]

On Thu, 23 May 2024 19:01:49 GMT, William Kemper <wkemper at openjdk.org> wrote:

> This change facilitates further extensions from this base class in the forthcoming generational mode for Shenandoah.

LGTM!

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Marked as reviewed by ysr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19372#pullrequestreview-2075245929