tests: Add unit tests infra for secp256r1

[chfast]

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[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.06%. Comparing base (ae93d5d) to head (f561daa).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
test/unittests/precompiles_secp256r1_test.cpp	90.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1326   +/-   ##
=======================================
  Coverage   87.06%   87.06%           
=======================================
  Files         168      169    +1     
  Lines       24788    24808   +20     
  Branches     4070     4074    +4     
=======================================
+ Hits        21582    21600   +18     
  Misses        547      547           
- Partials     2659     2661    +2     

Flag	Coverage Δ
eest-develop	84.15% <ø> (ø)
eest-develop-gmp	15.85% <0.00%> (-0.02%)	⬇️
eest-legacy	11.09% <0.00%> (-0.01%)	⬇️
eest-legacy-silkpre	17.58% <0.00%> (-0.02%)	⬇️
evmone-unittests	83.70% <90.00%> (+0.19%)	⬆️

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Components	Coverage Δ
core	93.53% <ø> (ø)
tooling	86.19% <ø> (ø)
tests	84.13% <90.00%> (+<0.01%)	⬆️

Files with missing lines	Coverage Δ
test/unittests/precompiles_secp256r1_test.cpp	90.00% <90.00%> (ø)

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