[GIT-PULLS] [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