chore(ds): require ext-ds v1

[simPod]

Summary

• Require ext-ds v1 in Composer
• Install ds-1.8.0 in GitHub Actions instead of the floating latest release
• Remove the php-ds polyfill dev dependency so dev installs require the native extension

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.93%. Comparing base (ddc699e) to head (d527ac4).

Additional details and impacted files

@@           Coverage Diff           @@
##            0.2.x      #89   +/-   ##
=======================================
  Coverage   85.93%   85.93%           
=======================================
  Files           6        6           
  Lines          64       64           
=======================================
  Hits           55       55           
  Misses          9        9           

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