Refactor crypto API

Currently the crypto API is rather limiting, as it binds the curve (or system) used for signing to the curve used to navigate bip32 whereas the 2 are independent.

An idea is to make a "System" trait where we can have this handled and we only expose a couple of functions like "get_public_key" and "sign"

This issue is not bound to any milestone as it's more of our wrapper crates improvement and is to be moved there when separate repos are made

🔗 zboto Link

It also doesn't allow to specify a chain code when generating a key, which is used by some projects.