RFR: 8339960: GenShen: Fix inconsistencies in generational Shenandoah behavior [v2]

[Y. Srinivas Ramakrishna]

On Mon, 16 Sep 2024 21:51:40 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> This pull request contains a backport of commit 1a7d597d from the openjdk/shenandoah repository.
>> 
>> The commit being backported was authored by Kelvin Nilsen on 13 Sep 2024 and was reviewed by William Kemper.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove dependency on utilities/checkedCast.hpp

Marked as reviewed by ysr (Committer).

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PR Review: https://git.openjdk.org/shenandoah-jdk21u/pull/90#pullrequestreview-2310406769