RFR: 8368499: GenShen: Do not collect age census during evac when adaptive tenuring is disabled

[Kelvin Nilsen]

On Wed, 24 Sep 2025 22:53:28 GMT, William Kemper <wkemper at openjdk.org> wrote:

> This is a simplification to `ShenandoahEvacTracker` (which is a diagnostic feature). The ability to compute the age census during evacuation was still in the code, even though the (experimental) option to enable it was removed. Removing the rest of the code allows us to take an additional flag-check off the evacuation path and to consolidate duplicated gc stat processing code between `shControlThread` and `shGenerationalControlThread`.

Thanks for these improvements.

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Marked as reviewed by kdnilsen (Committer).

PR Review: https://git.openjdk.org/jdk/pull/27479#pullrequestreview-3264977489