[php-src] PR #24568: RFC: array_partition()

Pull Request: https://github.com/php/php-src/pull/24568 Author: ayoubezzini Adds array_partition(), which splits an array into the elements that satisfy a callback and those that don't, in a single pass. RFC: https://wiki.php.net/rfc/array_partition (TBD) ## Spec ```php function array_partition(array $array, callable $callback, int $mode = ARRAY_FILTER_USE_VALUE): array ``` - Returns [$matching, $nonMatching]. - Keys are preserved, like array_filter(). - $mode accepts ARRAY_FILTER_USE_VALUE (0), ARRAY_FILTER_USE_KEY and ARRAY_FILTER_USE_BOTH, with the same semantics as array_filter(). Any other value throws a ValueError. - The callback's return value is evaluated with standard truthiness, like array_filter(). - Exceptions thrown by the callback propagate, and partial results are discarded. ## Example ```php [$adults, $minors] = array_partition($users, fn($u) => $u->age >= 18); ``` Today this takes either two array_filter() passes with a negated callback, or array_filter() followed by array_diff_key(). ## Implementation notes - The mode validation, callback invocation and element insertion of array_filter() were extracted into shared static helpers, so both functions behave identically. array_filter() performance is unchanged (within noise on a 1M-element benchmark). - Tests cover basic splitting, empty input, all/none matching, key preservation (int and string keys), ARRAY_FILTER_USE_KEY/ARRAY_FILTER_USE_BOTH, invalid modes, exceptions in the callback, and by-reference elements.