Use anyhow for error handling

[cchudant]

Replace all error handling with anyhow

I am debugging the madara <=> madara bootstrapper integration and ran into some errors that looked like this

thread 'main' panicked at src/contract_clients/config.rs:29:10:
called `Result::unwrap()` on an `Err` value: UrlParser
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

which were hard to debug, so I moved the entire crate to anyhow.

Now it's more like this

Error: Initializing client config

Caused by:
    0: Creating the Ethereum RPC client
    1: Failed to parse URL

with each layers adding more context to the errors.

A lot of the error handling here, especially the add to json errors and wait for transaction stuff are very very redundant though - but i think this needs a deeper refactoring than the surface level stuff I just did here.

[cchudant]

also the unwrap count is now 0 🥳