Remove PHPUnit from PHP images

v9.4 (currently what we use)

• EoL occurred on February 2, 2024
• Designed for PHP 7.3

https://phpunit.de/supported-versions.html

Docs:

• https://phpunit.de/announcements/phpunit-9.html
• https://phpunit.de/announcements/phpunit-10.html
• https://phpunit.de/announcements/phpunit-11.html
• https://github.com/sebastianbergmann/phpunit/blob/9.6/DEPRECATIONS.md
• https://github.com/sebastianbergmann/phpunit/blob/10.5/DEPRECATIONS.md
• https://github.com/sebastianbergmann/phpunit/blob/11.3/DEPRECATIONS.md

Things to start watching out for now:

• deprecation warnings generated by our current version

TODO:

• Any key benefits other than bug fixes/PHP 8.x specific support?
• Build images with 9.6 to do some preliminary tests against
• Build images with 10 to do some preliminary tests against
• Decide when/if 9.6 is feasible
  • How much will work will it take?
  • Is it even worth it?
• Decide when/if 10.x is feasible
  • How much will work will it take?
  • Is it even worth it?
• Decide when/if 11.x is feasible (can we skip 10.x or will that take too much work for now?) [>= PHP 8.2]
  • How much will work will it take?
  • Is it even worth it?

Review the PHP image definitions and current PHPUnit setup, then read the linked PHPUnit release and deprecation documentation. Compare preliminary builds and tests for PHPUnit 9.6, 10.x, and 11.x; done means the feasible version or removal path is documented with its required work and PHP compatibility.