Changes
- Drop PHP < 8.2, require PHP >= 8.2
- Implement __serialize/__unserialize (O: format), replacing Serializable (C:)
- Fix sort/ksort to accept null comparators (#134)
- Support nested sort comparators via FCI save/restore (#48)
- Guard allocate against negative capacity (#33)
- Update CI for PHP 8.2-8.5, PHPUnit 11 (#213)
- Remove legacy Serializable and pre-8.2 compat code