[php-src] PR #24022: ext/session: Close save handler when session encoding fails

Pull Request: https://github.com/php/php-src/pull/24022 Author: iliaal Since 86b49211577, a session that cannot be encoded (for example a $_SESSION key containing a pipe with the php serializer) makes session_write_close() return early without closing the save handler, so the files handler keeps the session file locked until the end of the request and concurrent requests for that session block on it. This only affects PHP-8.6 and master; 8.5 and earlier always reached the close. The handler is now closed on that return, like the rest of the function and session_regenerate_id() already do, including when an exception is pending, since the engine does not invoke a user close() callback in that state anyway. /cc @Girgias