RFR: Fix satb barrier for object array copy [v4]

[Aleksey Shipilev]

On Fri, 31 Mar 2023 16:19:04 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> The satb barrier for overwritten arrays residing in old-gen must be unconditional during young GC.
>> 
>> During old GC, the satb barrier is only needed for overwritten old-gen arrays if the array is below TAMS within its old-gen region.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Refinements requested by reviewers

Looks fine to me!

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Marked as reviewed by shade (Committer).

PR Review: https://git.openjdk.org/shenandoah/pull/237#pullrequestreview-1367237464