Type-stable compress and random order in benchmarks

[gdalle]

• Fix type-unstable compression to avoid getting a sparse matrix when the groups are empty
• Add random ordering to benchmarks, otherwise bicoloring results are useless

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (398490d) to head (32538cf).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #198   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           13        13           
  Lines         1603      1611    +8     
=========================================
+ Hits          1603      1611    +8     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.