RFR: 8350567: NMT: update VMATree::register_mapping to copy the existing tag of the region [v4]

[Thomas Stuefe]

On Mon, 3 Mar 2025 13:07:26 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> When committing a sub-region (SR) in the middle of a reserved region (RR), we need to decide on the MemTag. To find the correct tag, we had to find the RR base and take the tag and use it for SR.
>> With this PR, there will be no need to find the RR base and the tag of the previous region of SR can be copied to the SR.
>> 
>> Tests:
>> linux-x64-debug, gtest:NMT*, runtime/NMT
>
> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
> 
>   out tag of the begin node (stA) is used for accounting.

Good

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

Marked as reviewed by stuefe (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23771#pullrequestreview-2654385315