ICU-22956 Use InCB for grapheme cluster segmentation

[eggrobin]

Fix grapheme cluster segmentation, which had gone out of synch with the Unicode Standard because the derivation of InCB had changed in 16.0.

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22956
• Required: The PR title must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• Required: Each commit message must be prefixed with a JIRA Issue number. Example: "ICU-1234 Fix xyz"
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[eggrobin]

@markusicu I think this one will need byte flipping too.

[markusicu]

@markusicu I think this one will need byte flipping too.

done

[jira-pull-request-webhook]

Hooray! The files in the branch are the same across the force-push. 😃

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[markusicu]

@eggrobin this looks ready to merge; please do so unless you discovered something else to change

[eggrobin]

Yeah, it is ready, I just got distracted by a UTC meeting.