[php-src] PR #23017: ext/intl: Add SpoofChecker::getBidiSkeleton()

Pull Request: https://github.com/php/php-src/pull/23017 Author: LamentXU123 Follow up #13469. Since we have SpoofChecker::areBidiConfusable() with all these constant (UBIDI_LTR, UBIDI_RTL, UBIDI_MIXED and UBIDI_NEUTRAL) it can only determine whether two strings are visually confusable in a given text direction. Applications that need to detect confusable identifiers among a large existing set would otherwise need to repeatedly perform pairwise comparisons using areBidiConfusable(). Now since ICU 74+ and we have SpoofChecker::areBidiConfusable() already, it is convenient to add the corresponding SpoofChecker::areBidiConfusable() . ICU's bidi skeleton API transforms an identifier into a skeleton for a given text direction. So it is useful for larger compares. e.g. ```php $checker = new Spoofchecker(); $skeleton = $checker->getBidiSkeleton( Spoofchecker::LTR, $identifier ); if ($skeleton !== false && isset($knownSkeletons[$skeleton])) { // The identifier may be visually confusable with an existing one. } ``` The internal API is documented at: https://unicode-org.github.io/icu-docs/apidoc/dev/icu4c/uspoof_8h.html#a62055cfa692b3811341f9699fc8986a0