ci: check Moodle 4.3, PHP 8.2, strict phpdoc

[jrchamp]

• Add Moodle 4.3
• Use PHP 8.2 for 4.3 and newer
• Only run moodle-plugin-ci steps when the moodle-plugin-ci installs successfully
• On moodle-plugin-ci v4, set --max-warnings 0 for phpdoc
• If the job has been cancelled, mark the job as failed so that PR status checks cannot be bypassed
• Use !cancelled() instead of always() as recommended by GitHub

From https://docs.github.com/en/actions/learn-github-actions/expressions#always

If you want to run a job or step regardless of its success or failure, use the recommended alternative: if: ${{ !cancelled() }}

[smbader]

Onward and upward!