Remove async code and tokio from where it's not required

[cptartur]

We are using async code with tokio in the whole package just to make blocking calls to the rpc under the hood.
Instead, we should just be using rayon and handle async only where it's required - when making calls to the rpc.

Change the foundry code so it is not async anymore and user rayon instead.
We need to keep async and tokio only in places where we are making rpc calls.