ICU-22549 Add RuleBasedBreakIterator fuzzer

[FrankYFTang]

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22549
• Required: The PR title must be prefixed with a JIRA Issue number.
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
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• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[richgillam]

This feels like the bare minimum, but should be fine.

[richgillam]

This is almost always going to give you an error code saying the rule string is invalid. Maybe that's fine, but I wonder if we need a more devious test that takes advantage of knowing what the syntax of RBBI looks like.

Of course, that'd be a lot of work. I think this is probably fine for now, but we should think about smarter/more evil fuzz testing here for some time in the future.

[FrankYFTang]

I think the purpuse for fuzzing is the data is power by AI and try to generate input that is "unexpected" by the programmer to make sure during that condition the code won't break but return error. The smart of the fuzzing is based on the fuzzer and I will leave that smart to the AI to do it. The AI might be able to see all the branching in our code and figure out how to generate better fuzzing data to attack those (if not, then it is not a good AI)