refactor(bls12-381, bls12-377): MillerLoopFixed corresponds to gnark

[yelhousni]

Description

Similar to #506 for BLS12-377 and BLS12-381.

Type of change

• New feature (non-breaking change which adds functionality)

How has this been tested?

Existing tests pass.

+ [BLS12-*] Pair should output the same result with MillerLoop or MillerLoopFixedQ: OK, passed 100 tests.

How has this been benchmarked?

Please describe the benchmarks that you ran to verify your changes.

Lines precomputations should be faster, but this is a one-time computation.

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[ivokub]

LGTM