Refactor: re-introduce points in KZG verification key

[yelhousni]

Description

Re-introducing points G1, G2 and [α]G2 in KZG verification key after #466. This is needed in the Solidity Plonk verifier in gnark. My initial thought was to hardcode the values of the points' coordinates in solidity instead of calling the KZG package, but apparently (cc @ThomasPiellard) Linea (and Aztec) use a different G1 point than (1,2) for BN254. We should also then use ScalarMultiplication(x, G1) instead of ScalarMultiplicationBase(x). Anyway it should be flexible for users now.

Type of change

• Bug fix (non-breaking change which fixes an issue on gnark side)

How has this been tested?

Same current tests.

How has this been benchmarked?

NA

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