Tweak parameters in regression yaml

[lintool]

• simplified parameters in cases where there are default (for BEIR)
• moved "threads" parameter up closer to beginning of command (for indexing, all regressions)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.18%. Comparing base (859c7bb) to head (27d59c5).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #2581   +/-   ##
=========================================
  Coverage     67.18%   67.18%           
  Complexity     1480     1480           
=========================================
  Files           219      219           
  Lines         12700    12700           
  Branches       1530     1530           
=========================================
  Hits           8533     8533           
  Misses         3640     3640           
  Partials        527      527           

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