perf: optimize curve membership test

[yelhousni]

Description

This PR optimizes the curve membership test IsOnCurve() for all curves on both G1 and G2, by:

• saving 1 Fp mul
• specializing the multiplication by the curve coefficient b

Type of change

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

How has this been tested?

Old TestG1AffineIsOnCurve and TestG2AffineIsOnCurve

How has this been benchmarked?

e.g. BLS12-381 on AWS z1d.large:

G1 335 ns vs. 190.6 ns
G2 624 ns vs. 495.3 ns

Compared to geth/kilic (cc @asanso, @MariusVanDerWijden):
G1 320.7 ns vs. 190.6 ns
G2 917.9 ns vs. 495.3 ns

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