feat: add IsOnG2 for BN254

[ivokub]

Description

This method allows to check for non-membership. In case we need to assert membership it is still more efficient to use AssertIsOnG2 as then we don't have to call IsZero for non-native elements which is more expensive that AssertIsEqual.

@yelhousni - can you recommend better naming for the methods? I think this could generalize to other curves, but right now needed for Linea, so omitted the implementation.

Type of change

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

How has this been tested?

• TestIsOnTwistSolve
• TestIsOnG2Solve

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

[yelhousni]

LGTM