Improve the support for new(er) versions of PHP in Moodle LMS.

The current timeline is:

• PHP 8.1 - Moodle 4.1.2 - DONE
• PHP 8.2 - Moodle 4.2.3 & 4.3.0 - DONE
• PHP 8.3 - Moodle 4.3.x TBC

Note: The release date of Moodle 4.3 is 9th October, 2023. The current planned release date for PHP 8.3 is 23 November, 2023. RC1 for PHP 8.3 was release 31 August 2023. As of 14 September 2023, there has not been anything identified in PHP 8.3 that Moodle isn't compatible over the top of 8.2.  Therefore it is likely that the first minor release of Moodle 4.3 that is released after the PHP 8.3 release will be 8.3 compliant.