Rely on `RPC_URL` instead of `foundry.toml` configuration

[MerlinEgalite]

Perhaps it's better to set the RPC_URL and use it instead of the foundry.toml configuration because it's likely that someone pushed here credential while if it's in the .env file it's ignored. What do you think?

And we can just check that if the .env variable is empty we fallback to https://eth.llamarpc.com