RFR: 8365675: Add String Unicode Case-Folding Support [v4]

[Roger Riggs]

On Thu, 23 Oct 2025 18:32:03 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> Xueming Shen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   test case update
>
> test/micro/org/openjdk/bench/java/lang/StringCompareToFoldCase.java line 57:
> 
>> 55:     public String supLower = "\ud801\udc28\ud801\udc29\ud801\udc2a\ud801\udc2b\ud801\udc2c";
>> 56: 
>> 57:     @Benchmark
> 
> Add cases also for strings to themselves (latin1, utf16) to see how the fastest path compares.
> 
> Is there any body of more representative text with more typical intermixing of normal and folded sequences?  Strings with multiple ßß are not typical.

These will run a long time, consider reducing cases that are very similar.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27628#discussion_r2456661817