better import for libsecp256k1

[lorbax]

As suggested by @Fi3 in the review of #737, we should

1. move the dependency of secp256k1 in stratum_common and import this library from there
2. avoid to import secp256k1 in roles (it is used by the JDS for signing tokens and by the pool for verifying tokens' signature). Rather, some sort of wrapper structure in roles-logic for making and verifying signatures would be more appropriate.

[rockcoolsaint]

I think this is something I can handle. Can I go ahead with it? @lorbax

[lorbax]

Don't know if it is really a good "first issue" but if feel comfortable you can DM on discord and discuss how to proceed

[Fi3]

now you can import libs from the workspace Cargo.toml and refer to it in the crate Cargo.toml when you have common dep between crates in the same workspace.

[rockcoolsaint]

Don't know if it is really a good "first issue" but if feel comfortable you can DM on discord and discuss how to proceed

What's your discord handle?

[plebhash]

closed via #894