RFR: Fix satb barrier for object array copy [v2]

[Kelvin Nilsen]

> 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:

  Fix typo in comment

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/237/files
  - new: https://git.openjdk.org/shenandoah/pull/237/files/1ce3bf5e..883ab7c3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=237&range=01
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=237&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/shenandoah/pull/237.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/237/head:pull/237

PR: https://git.openjdk.org/shenandoah/pull/237