precompiles: Implement EIP-2537's bls12_g2mul

[rodiazet]

Implementation of the bls12_g2mul precompile: E2 affine point's multiplication from BLS12-381 curve according to the EIP-2537 spec https://eips.ethereum.org/EIPS/eip-2537#abi-for-g2-multiplication.

Depends on #995

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.97%. Comparing base (39aec66) to head (347c4f5).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #999      +/-   ##
==========================================
+ Coverage   93.94%   93.97%   +0.03%     
==========================================
  Files         147      147              
  Lines       15553    15580      +27     
==========================================
+ Hits        14611    14642      +31     
+ Misses        942      938       -4     

Flag	Coverage Δ
eof_execution_spec_tests	17.41% <0.00%> (-0.04%)	⬇️
ethereum_tests	27.59% <0.00%> (-0.05%)	⬇️
ethereum_tests_silkpre	19.32% <0.00%> (-0.04%)	⬇️
execution_spec_tests	19.31% <70.00%> (+0.10%)	⬆️
unittests	88.95% <66.66%> (-0.03%)	⬇️

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Files with missing lines	Coverage Δ
lib/evmone_precompiles/bls.cpp	100.00% <100.00%> (ø)
test/state/precompiles.cpp	91.22% <100.00%> (+1.99%)	⬆️
test/unittests/precompiles_bls_test.cpp	100.00% <100.00%> (ø)