[12.x] Consistent use of mb_split() to split strings into words (#56338)

* consistent use of mb_split to split strings into words with multi-byte support * The $pattern argument doesn't use /pattern/ delimiters, unlike other regex functions such as preg_match

Author: shaedrich

src/Illuminate/Support/Str.php

@@ -1402,7 +1402,7 @@ public static function title($value)
  */
  public static function headline($value)
  {
- $parts = explode(' ', $value);
+ $parts = mb_split('\s+', $value);
 
  $parts = count($parts) > 1
  ? array_map([static::class, 'title'], $parts)
@@ -1435,7 +1435,7 @@ public static function apa($value)
 
  $endPunctuation = ['.', '!', '?', ':', '—', ','];
 
- $words = preg_split('/\s+/', $value, -1, PREG_SPLIT_NO_EMPTY);
+ $words = mb_split('\s+', $value);
 
  for ($i = 0; $i < count($words); $i++) {
  $lowercaseWord = mb_strtolower($words[$i]);
@@ -1638,7 +1638,7 @@ public static function studly($value)
  return static::$studlyCache[$key];
  }
 
- $words = explode(' ', static::replace(['-', '_'], ' ', $value));
+ $words = mb_split('\s+', static::replace(['-', '_'], ' ', $value));
 
  $studlyWords = array_map(fn ($word) => static::ucfirst($word), $words);