Performance debugging mk. 2

[ml-evs]

Follow-up to #1836 and #1835 that adds timing instruments to our old tests, to see what is causing the problem.

[codecov]

Codecov Report

Merging #1837 (a868e6e) into master (f28a6e1) will decrease coverage by 0.05%.
Report is 21 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1837      +/-   ##
==========================================
- Coverage   90.77%   90.72%   -0.05%     
==========================================
  Files          74       75       +1     
  Lines        4629     4605      -24     
==========================================
- Hits         4202     4178      -24     
  Misses        427      427              

Flag	Coverage Δ
project	90.72% <ø> (-0.05%)	⬇️
validator	90.18% <ø> (-0.49%)	⬇️

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see 43 files with indirect coverage changes