RFR: 8339531: Improve performance of MemorySegment::mismatch [v10]

[Per Minborg]

On Fri, 6 Sep 2024 11:52:35 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR proposes to improve the performance of `MemorySegment::mismatch` by using Java code rather than transitioning to native code.
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use unaligned ops and rename benchmarks

I've added manual loop-unrolling for Aarch64 (only). This gives a significant performance boost for larger segments:

![image](https://github.com/user-attachments/assets/e477e4a6-8d4d-403d-91f8-978496f10021)

On x64, manual unrolling is not necessary.

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PR Comment: https://git.openjdk.org/jdk/pull/20848#issuecomment-2345784880