Upgrade site to PHP8

[thetwopct]

• Our current version PHP 7.4. PHP 7.4 has reached its end of life on November 28th, 2022.
• Pantheon now support PHP8.
• PHP 8 receives security updates until 26 Nov 2023.
• WordPress does not officially support PHP8 yet, although they say they are "mostly compatible"
• Plugins have varied PHP8 support, we would need to test each one

Test and evaluate the ability to update.

[cjyabraham]

I may need to upgrade to PHP 8 in order to take advantage of php-yaml which seems installed on the PHP 8 version of Pantheon but not our current PHP 7.4 version. Affects #757 and our ability to import and parse a yaml file.

Chat from Pantheon:

As per checking, these are the PHP version that has it enabled:

PHP 8.2: https://v82-php-info.pantheonsite.io/
PHP 8.1: https://v81-php-info.pantheonsite.io/
PHP 8.0: https://v80-php-info.pantheonsite.io/

This is the PHP version that does not have it installed:

PHP 7.4: https://v74-php-info.pantheonsite.io/

[cjyabraham]

I will try upgrading to php 8.1, as per the recommendation on this page.

• [x] CNCF
• [x] LFEvents
• [x] LFAsia
• [x] CNCF Presentations

[cjyabraham]

All upgraded.