Bumped ICU4N to 60.1.0-alpha.440

[NightOwl888]

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Fixes #998

Description

This bumps ICU4N to 60.1.0-alpha.440 which contains the Normalizer2 concurrency patch in NightOwl888/ICU4N#122 that addresses the problems with random failures of TestICUNormalizer2CharFilter.TestRandomStrings() in concurrent environments.

ThaiTokenizer

I made an attempt at documenting the "differences" between how ThaiTokenizer behaves and how ICUTokenizer behaves with Thai text. However, after adding several tests to check how they deal with transitions between Thai and non-Thai words and numerals, it turns out they behave identically in all cases I checked. I ended up temporarily replacing the ThaiTokenizer with the implementation of ICUTokenizer and discovered that all of the tests pass. So, the ThaiWordBreaker effectively is a poor-man's way of implementing part of the UAX #29 http://unicode.org/reports/tr29/ spec, but we cannot guarantee that it does completely comply for the Thai language.

I ended up adding documentation explaining that it does not guarantee to be compliant with the Unicode spec and recommended to use ICUTokenizer instead. But I am wondering whether we should just rewire the ICUTokenizer into the ThaiTokenizer and eliminate the "JDK compatible" attempt that is not guaranteed to be compatible with the JDK, anyway.

The JDK RuleBasedBreakIterator behaves differently across different vendors and versions, so there really is no stable target to hit, anyway. Some implementations don't even include a dictionary-based BreakIterator implementation, so Thai tokenization is impossible. Historically, this is one of the main motivations for creating the lucene-analysis-icu package which guarantees stability across JDK versions.

[paulirwin]

Approved; note the typo that is failing the pre-commit check. Once fixed looks good to merge.