`PHP 8.3` support.

[terabytesoftw]

Hi, we should consider upgrading the PHP version in the master branch. Running PHPUnit 4 to accommodate new PHP versions has become quite cumbersome due to the need to patch PHPUnit, which sometimes leads to unexpected errors. By raising the minimum required PHP version to at least 8.1, in my opinion, we can update our packages without breaking backward compatibility. In my tests with branch 2.2, i found that PHP 8.3 is entirely compatible. Those who need to use versions older than 8.1 can continue using 2.0.49, as suggested by @rob006 #19831 (reply in thread).

This would, in some way, allow us to maintain the code more easily and address bugs more effectively.

Test php 8.3: #19953

@yiisoft/yii2, @yiisoft/reviewers