RFR: Fix satb barrier for object array copy

[Kelvin Nilsen]

On Wed, 29 Mar 2023 23:54:25 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.

I want to make a change to the code and retest before removing draft status.

-------------

PR Comment: https://git.openjdk.org/shenandoah/pull/237#issuecomment-1489488252