crypto: Avoid to/from Montgomery conversion of y in secp256k1

[chfast]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.15%. Comparing base (401ce72) to head (93427d0).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1303      +/-   ##
==========================================
- Coverage   87.15%   87.15%   -0.01%     
==========================================
  Files         167      167              
  Lines       24745    24744       -1     
  Branches     4059     4059              
==========================================
- Hits        21567    21566       -1     
  Misses        537      537              
  Partials     2641     2641              

Flag	Coverage Δ
eest-develop	17.82% <0.00%> (+<0.01%)	⬆️
eest-develop-gmp	15.85% <0.00%> (+<0.01%)	⬆️
eest-fusaka	12.22% <0.00%> (+<0.01%)	⬆️
eest-legacy	11.11% <0.00%> (+<0.01%)	⬆️
eest-legacy-silkpre	17.71% <100.00%> (-0.01%)	⬇️
eest-static	18.74% <100.00%> (-0.01%)	⬇️
evmone-unittests	83.76% <100.00%> (-0.01%)	⬇️

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Components	Coverage Δ
core	93.30% <100.00%> (-0.01%)	⬇️
tooling	88.35% <ø> (ø)
tests	84.12% <ø> (ø)

Files with missing lines	Coverage Δ
lib/evmone_precompiles/secp256k1.cpp	100.00% <100.00%> (ø)

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