chore(ci): add PHP 8.5 to CI workflows

[phil-davis]

PHP 8.5 works, use it in CI.

Only run php-cs-fixer on the oldest supported PHP 7.4 (when run with PHP 8.* it now tries to apply PHP 8.* code changes, which we don't want just yet)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.19%. Comparing base (c98a110) to head (a0181ba).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #259      +/-   ##
============================================
- Coverage     94.24%   94.19%   -0.05%     
  Complexity      262      262              
============================================
  Files            15       15              
  Lines           886      879       -7     
============================================
- Hits            835      828       -7     
  Misses           51       51              

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[phil-davis]

That works OK. I will leave this to merge after PHP 8.5 is officially released in Nov 2025.

https://wiki.php.net/todo/php85