perf: subgroup check

[yelhousni]

Description

use mulWindowed instead of ScalarMultiplication is G1 and G2 subgroup membership and cofactor clearing methods.
1- The point is still purported to be in the prime subgroup where GLV applies
2- multiplying by a small constant is faster with mulWindowed

N.B.: multiplying e.g. twice by x0 is faster than multiplying by x0^2 because it has smaller Hamming weight. E.g. for BLS12-381, mul-by-x0 is 64 dbl + 6 mul while mul-by-x0^2 is 128 dbl + 17 mul. There is still room for improvement if needed by specialising mul-by-x0 using a short addition chain.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How has this been tested?

Same tests.

How has this been benchmarked?

• BLS12-38

benchmark                        old ns/op     new ns/op     delta
BenchmarkG1JacIsInSubGroup-2     59891         46740         -21.96%

benchmark                        old ns/op     new ns/op     delta
BenchmarkG2JacIsInSubGroup-2     74121         55710          -24.84%

• BN254

benchmark                        old ns/op     new ns/op     delta
BenchmarkG2JacIsInSubGroup-2     58285         48690        -16.46%

• BW6-761

benchmark                        old ns/op     new ns/op     delta
BenchmarkG1JacIsInSubGroup-2     410121        322322        -21.41%

benchmark                        old ns/op     new ns/op     delta
BenchmarkG2JacIsInSubGroup-2     410955        322196        -21.60%

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