feat(`cheatcodes`): add `vm.ec{Add, Mul?, AddP256, MulP256?}` (elliptic-curve cryptography)

[StackOverflowExcept1on]

Component

Forge

Describe the feature you would like

It would be great to have such methods in vm since in rollups we could see more complex smart contracts that use secp256k1 / secp256r1 elliptic-curves. Intended use case - multi-signature schemes, ECDH on-chain, etc.

Additional context

Mul is marked with a question mark because we already have vm.createWallet(uint256 privateKey) and vm.publicKeyP256(uint256 privateKey), but we don't have any generic method like add/mul that returns struct PublicKey { uint256 x, y; }.

[0xrusowsky]

@StackOverflowExcept1on aren't you able to use solidity libraries for those? if not, we could discuss further

[StackOverflowExcept1on]

@0xrusowsky this is literally what I'm doing now (https://github.com/StackOverflowExcept1on/frost-secp256k1-evm/blob/master/src/utils/cryptography/Secp256k1Arithmetic.sol), but it would be useful to have built-in cheatcodes for this since the same secp256k1 curve is the standard for Ethereum.

[grandizzy]

@StackOverflowExcept1on @0xrusowsky I think would be OK to have a built-in cheatcode for such too, @zerosnacks wdyt?

[zerosnacks]

I wouldn't be against this only note is that we have to be absolutely sure of the implementation of the cryptography. An implementation using k256 (a dependency we already use) seems straightforward. Regarding the naming, it needs to be specific enough to be future proof so perhaps .secp256k1 rather than .ec?

[StackOverflowExcept1on]

Ok, I'd like us to design API for this feature.