feat: accept signer trait impl instead of LocalWallet

[piotrostr]

This change allows to use other signer types, like remote signers, or secure envelope providers (Privy, Magic, etc) for the Secp256k1 signatures

There is minimal migrational overhead, the trait is implemented in signer/mod.rs for the LocalWallet, only requires wrapping it with atomic reference counter (Arc) due to dynamic object size of the struct implementing the trait

This could be extended with KMS like Hashicorp Vault etc, in our use-case it comes down to enabling Privy

This change also adds serde::Serialize for the InfoClient types for better composability