[php-src] PR #23970: ext/pdo: Keep prior bindings when execute() fails to bind its array

Pull Request: https://github.com/php/php-src/pull/23970 Author: iliaal PDOStatement::execute() dropped the existing bindings before binding its array argument, so when an entry failed part-way through, for example a value whose string conversion throws, the entries bound so far stayed installed and the next execute() without arguments ran with them. The new table is now built separately and installed only once every entry is bound. This also stops a __toString() that re-executes the statement from freeing the table being filled.