[php-src] Issue #24449: Interned strings are not flagged as IS_STR_VALID_UTF8

Issue: https://github.com/php/php-src/issues/24449 Author: rr-it ### Description Interned strings were flagged as IS_STR_VALID_UTF8 in general - introduced by https://github.com/php/php-src/commit/64127b66c64457d6356d06bb517c35f72fa74852 https://github.com/php/php-src/blob/64127b66c64457d6356d06bb517c35f72fa74852/Zend/zend_string.c#L194-L198 Later on in the PHP 8.3.0 development cycle this feature was removed - without any mentioning in commit message - by https://github.com/php/php-src/commit/99b86141ae36633dce70e202d9fe75c73996097d https://github.com/php/php-src/blob/99b86141ae36633dce70e202d9fe75c73996097d/Zend/zend_string.c#L194-L196 https://github.com/php/php-src/blob/54ac0b992852943e33a00f3e4704e48d7a07c6a1/Zend/zend_string.h#L95-L97 Shall this be reverted? Also see https://github.com/php/php-src/issues/24380 ### PHP Version ```plain Introduced and removed in PHP 8.3.0 early development. ``` ### Operating System _No response_