RFR: Use distinct "end of cycle" message for each Shenandoah pause

[Kelvin Nilsen]

On Tue, 2 May 2023 22:54:53 GMT, William Kemper <wkemper at openjdk.org> wrote:

> This change allows the `GarbageCollectionNotificationInfo::gcAction` to be overridden. Shenandoah now uses this to distinguish the notification raised for each of the pauses during the concurrent cycle. This will make it easier for monitoring software to identify which phases may be having longer than expected pauses.

src/hotspot/share/gc/shenandoah/shenandoahVMOperations.cpp line 82:

> 80: 
> 81: void VM_ShenandoahFinalRoots::doit() {
> 82:   ShenandoahGCPauseMark mark(_gc_id, SvcGCMarker::CONCURRENT);

Why are we disabling the aging of regions?  And why are we disabling the aging cycle?

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/270#discussion_r1183122172