RFR: 8328112: Remove CardTable::_guard_region

[Thomas Schatzl]

On Fri, 15 Mar 2024 08:06:24 GMT, Guoxiong Li <gli at openjdk.org> wrote:

> Hi all,
> 
> This patch removes the `CardTable::_guard_region`. Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxiong

The change should also remove the allocation of the extra page in the first few lines of `CardTable::initialize`.

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Changes requested by tschatzl (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18324#pullrequestreview-1938662378