Remove deprecated backticks (#471)

* feat: Bumping supported php Version and adjusted dependencies to install with PHP 8.5

* feat: replace deprecated backtick operators with `shell_exec` functions

* Fix code styling

* feat: Nevermind, don't mess with supported versions

* feat: fixed the test workflow.

`cachewerk/relay` was not installing in PHP 8.5 causing tests to fail (The extension relay was present so the tests were not skipped)

* feat: Fixed type errors reported by PHPStan

* Fix code styling