Use ini_get_all() to retrieve compiled-in default value of INI setting

[sebastianbergmann]

Uses php/php-src#22134 as described in php/php-src#22133 and motivated by #97 (comment).

[codecov]

Codecov Report

❌ Patch coverage is 46.15385% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.42%. Comparing base (a15fa79) to head (f308ab1).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/Runtime.php	46.15%	7 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #98      +/-   ##
============================================
- Coverage     46.44%   46.42%   -0.02%     
- Complexity      105      114       +9     
============================================
  Files             3        3              
  Lines           211      224      +13     
============================================
+ Hits             98      104       +6     
- Misses          113      120       +7     

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