refactor: separate crate for wallets logic

[klkvr]

Motivation

Extracts wallet logic to separate crate to make it more resusable. After that it will be possible to add foundry-wallets as a dependency of foundry-cheatcode to support unlocking and using wallets directly from cheatcodes

[mattsse]

I like this!

this unblocks us from turning this into an actually usable crate eventually

I think we can push more code from the wallet command impl to the wallet crate

[DaniPopes]

LGTM, but this does add clap and other dependencies earlier. This might not matter much , and I don't see a way around this without duplicating structs.

[mattsse]

yeah, I only see this as an intermediary issue, because I think we want this crate to be more like a library and then move the clap types back to the cli crate.

but this is a less invasive first step in that direction