RFR: 8286829: Shenandoah: fix Shenandoah Loom support [v3]

[Aleksey Shipilev]

On Wed, 1 Jun 2022 13:48:32 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> Both `obj->is_instance()` and `obj->is_stackChunk()` in `relativize_stack_chunk` checks the same Klass::_kind field, so I would be surprised if you would be able to find a perf regression here. We checked the marking times before and  after adding relativize_stack_chunk, and couldn't see any difference.
>
> Thanks for your insights, @stefank

All right then!

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

PR: https://git.openjdk.java.net/jdk/pull/8924