[php-src] Issue #12561: `\IntlDateFormatter` constructor throws an exception for unknown locales since 8.1.25

Issue: https://github.com/php/php-src/issues/12561 Author: mpdude ### Description Since PHP 8.1.25 and due to the changes in #12282, the following code now throws an IntlException: ```php <?php new IntlDateFormatter( 'xx', IntlDateFormatter::FULL, IntlDateFormatter::FULL, null, null, 'w' ); ``` There may be many reasons why the locale value is invalid – it might be taken from the LANG environment variable and be set to C, it might be parsed from request parameters (the reason behind #12533), or it might be a locale name that is valid on one system but is not in the list of generated/supported locales on another system. While I agree that ideally, all these conditions should be checked and caught beforehand, and I also agree that fixing #12282 without a sensible locale to assume might be difficult, my point is that turning this condition into an exception in a bugfix release is a breaking change that should be reverted. ### PHP Version PHP 8.1.25 ### Operating System _No response_