[php-src] PR #25159: ext/pdo_dblib: Release persistent handle error strings at request end

Pull Request: https://github.com/php/php-src/pull/25159 Author: iliaal The DB-Lib message and error handlers estrdup() server text into the connection's error state, and on a persistent connection an error raised through PDO::exec() (or, since GH-23741, the transaction calls and lastInsertId()) stays there past the end of the request, so the next request or the handle close at shutdown efree()s pointers into a reset request heap. A persistent_shutdown handler now frees them once the last PDO object using the connection is released, the same refcount check pdo_dbh_free_storage() uses before rolling back; keeping the strings persistent instead would let a later timeout report the previous request's message.