... when enable V8_COMPRESS_POINTERS_IN_ISOLATE_CAGE.
When enable V8_COMPRESS_POINTERS_IN_ISOLATE_CAGE and
V8_EXTERNAL_CODE_SPACE, because of the external code space,
we could not get the isolate using RoundDown directly, which
may cause wrong isolate address. We should use memory chunk
like in V8_COMPRESS_POINTERS_IN_SHARED_CAGE instead.

Bug: v8:12664, v8:12715
Change-Id: Ib78770fdb66fa509d6d8acc836803ec9d6804ef1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3532599Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: 王澳 <wangao.james@bytedance.com>
Cr-Commit-Position: refs/heads/main@{#79774}