RFR: 8328220: GenShen: Move generational mode operational parameters out of ShenandoahHeap [v2]

[Y. Srinivas Ramakrishna]

On Tue, 19 Mar 2024 16:40:13 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> * Many fields previously defined in `ShenandoahHeap` have been moved to `ShenandoahOldGeneration`.
>> * Generational specific serviceability has been moved to `ShenandoahGenerationalHeap`.
>> * Methods for sizing the old generation have been moved to `ShenandoahGenerationalHeap`.
>> * `ShenandoahGenerationalHeap::heap()` now asserts that the generational mode is active.
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Improve comments, make more variables const.

Rereviewed; thanks for taking care of the feedback!

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Marked as reviewed by ysr (Committer).

PR Review: https://git.openjdk.org/shenandoah/pull/406#pullrequestreview-1947290769