[php-src] Issue #12457: `zend_memnistr` results are incorrect under certain conditions

Issue: https://github.com/php/php-src/issues/12457 Author: SakiTakamachi ### Description The following code: ```php <?php var_dump(stripos('aaBBBBBbb', 'b')); ``` Resulted in this output: ``` int(7) ``` But I expected this output instead: ``` int(2) ``` This occurs when the following conditions are met: - $needle is single character - (Number of characters from the first lowercase letter to the end) >= (Number of characters from the beginning to the first uppercase letter) - Uppercase letters appear before lowercase letters ### PHP Version PHP8.2+ ### Operating System any