Replace secp256k1 library about curv

[namuyan]

Hello, it looks good experiment!
I checked fastecdsa, Python library implemented C, using same GMP library.
When I compare with it, I feel 10 times slower performance on multiply scalar and point.

[elichai]

I would prefer https://github.com/RustCrypto/elliptic-curves/tree/master/k256 or something based on fiat-crypto.

but even then it's quite scary, as libsecp256k1 is very battle tested.
another option would be to fork libsecp256k1 and write bindings to the internal functionality, that allows infinity, jacobian points and more.